Here's some tech articles I wrote for the IZCC.
 
 
Autobody Paint Tech 101: 
First some clarifications:  A "Paint Store" is not your local NAPA.  Find a Paint store!  NAPA is good for small quantities, but they do not mix paint.  You will find your best selection at a Pro paint store. 
There are many manufactures of paint. 
I use PPG Starbase or DBC or DBU as a basecoat.    Starbase is lacquer.  DBC is better.  DBU is best, adding a catalyst to the thinner (reducer) to make the base color chemically cure.  Some painters like other brands.  The important thing to remember is to use the same manufacturer throughout the process.  If you use X brand primer, use X brand clearcoat.  Keep it consistent.  The chemical composition of it all is very important.  I like PPG (the most expensive).  This article will use PPG products, because I am familiar with them.  One thing about painting a car,  the bodywork labor is at least 50% of the price of the job.  That leaves 50% for materials.  Why scrimp on the materials?  Use the best you can afford! 

The paint store salesmen are your friends.  They are highly trained on all the products they sell.  They can teach you about paint.  Ask for it!  A motivated paint store salesman will teach you about his products.  He sells more paint that way.  I once had a Tech take me around back and teach me how to color sand and buff on a fresh black paint job on my 440Z Cabrio..  I have since bought $500 worth of sandpaper and buff compound/pads from that store….not including paint. 

1.  Bodywork.  Walk around the car and look at it.  Park it in the sunlight and close your eyes.  Feel along the car and sense the difference in the surface temperature of the metal. The bondo will be colder than  the metal.  Mark or remember the cold and low spots.  Your fingers and palm will be a better judge of low spots than your eyes.  The old magnet trick works to find filler, if you remember that the magnetic properties of the substrate are all relative to the bare metal.  There is a calibrated magnetic gauge available that tells you the thickness of the paint, available at paint stores. 
Do the bodywork.  You may need a dual action orbital (DA sander).  There are two kinds, Electric and Air powered.  Air ones use a minimum of a 3 horse 20 gallon compressor. Expect your compressor to run nonstop whilst sanding.  I use an electric DA sander, made by Porter Cable.  I don't have to fire up a 15 amp (110v) compressor to run a 1 hp sander.  Electric DA sanders are very quiet.  Some have dust attachment hoods that use an shop vac to collect the sanding dust.    Dig out the low spots and the bondo spots.  Any filler in your car is either old and inferior, or fresh and poorly done.  ASSUME IT!  This is the one time that you will not "make an ASS out of U and ME". 
Dig out the old filler.  This includes any lead in the factory body joints.  The lead may stain your topcoat.  Modern fillers are awesome, with none of the problems of old. 

Feather edge it.  Scratch up the metal good with 36-80 grit on your DA.  You can do this with the DA or by hand.  Apply the filler to an area at least 4x the size of the repair.  Grab a 16"  "longboard" sanding board armed with 80 grit and sand the area you filled.  Get it reasonably smooth (feel it with your hands). 

Sandpaper comes in two weights.  One grade fills quickly, the other  lasts a lot longer; but costs more.  I use the better grade to save money in the long run…. 

You gotta have tools!  You will need a compressor.  I have gotten by with a 3 hp 20 gallon for the past 10 years.  A air powered DA will make it run nonstop.  You will also need a paint gun.  There is no reason to buy a traditional siphon feed (cup on the bottom) gun.  They are inefficient.  The air pressure needed to feed the paint is between 40-80 psi.  At this rate, there is a lot of overspray.  These guns are virtually outlawed in California, as they waste so much paint and blow it into our air.  There is a new Sheriff in town, and his name is HVLP (or High Volume/Low Pressure).  These guns have an increased "Transfer Efficiency" and reduce overspray by 20-50%.  This directly impacts your pocketbook, as you buy less paint at the store.  HVLP guns need a lot of air volume, and my little 3 hp 20 gal does not keep up with it.  Another option is a gravity feed gun, either in a HVLP or non-HVLP setup.  The non-HVLP guns still have the high efficiency , as they do not need any air pressure to get the paint out of the gun.  A gravity feed gun has the paint cup on top.  It flows out on its own.  The air pressure is only there to atomize it.  These guns are very cheap at Harbor Freight (1800 423-2567 $40?).  At this price, you can affords to throw away the gun after every job, although mine are going on 2 yrs old and 20 cars.  I have found that my little compressor will keep up with a gravity feed or a siphon feed gun because you are not spraying continuously.  Refilling the cup gives the compressor time to recharge, as does walking around the car.  There are also mini guns out that fit in a door jamb, or can be used for those smaller jobs.  I can't stress enough the value of a gravity feed gun.  It saves paint, reduces overspray, and gives consistent show quality jobs.  I even paint my house with it.  The cup on top design makes cleanup a breeze.  It can go in the dishwasher if you are using water-borne paints or housepaint. 
 
  Sanders.  There are many different types to use, depending on what you are doing.  The 6" pad DA is the most common.  The 8/9" tractor is a big bondo hog, slowly smoothing out large areas at once.  The 16" air powered straight line sander and the 16" long board hand sander are great for making large areas flat and straight.  When in doubt, use the hand tool instead of the air tool.  The results will be much better.  The general chain of events is to grind/sand with a 6" DA, then do the filler work.  The filler can be knocked down with a tractor, DA, or straight line sander.  After you get it close, switch to hand tools for accuracy.  I use 80 grit at this stage to quickly get the shape I need.  Somewhere in your process you will need to blow on some primer and sand it smooth to check your work.  I like to put a mist of black over the primer and sand that off.  Any low spits show up as black.  As you get closer to the finished primer surface, you will need to switch to 240 then 400 grit wet/dry paper.  This does not come in 16" board lengths, so you'll need a 1/4 sheet rubber block.  This 5" long block is not very accurate for getting panels flat, which is why we saved it for last, after the big 16" board did its job.  The 5" will smooth the existing surface and detail out the corners, edges, ect…Your paint store will have a huge selection of sanding tools.  The final sanding step is to have 400 or 600 grit scratches over the entire car.  This grit will not show up on the clearcoat, but is rough enough for the paint to grab onto. 
 
Clearcoat.  Urethane is in.  A decent clearcoat job will be as shiny and deep as the old lacquer jobs.  Lacquer is out.  I believe it is completely banned in CA now.  When I left in '95, all that was left on the shelf was primer, sold as a 'precoat".  Urethane clears can be sanded and buffed to a mirror finish, if you like.  They are very durable, and have UV inhibitors.  Great stuff.  The neat thing about a clearcoat job is that the basecoat color goes on like lacquer.  You can sand it in the booth, if you get a boo-boo.  It dries fast, too. 

Wax (not!). Flame on, Wax Salesmen!  The paint mfgs say don't wax for 30 days.  Don't ever ever use 5 Year Miracle Wax on a fresh job.  Don't listen to me, ask the paint tech at your paint store. 

Carwash -by hand.  Make your shine last. 

The Ballet dance follows:  The "Dance of the Painter" is the most difficult part of the job, and the most expensive.  The surface needs to be free of all oil.  Your hands have oils.  Wear gloves.  Never allow a shop rag to enter your booth or touch your car from the first sanding stroke.  Buy a roll of Bounty.  My process is as follows.  I wash the car with water only and pull it into the booth.  Kick on the fans and let it dry out.  Start wiping down the car with lacquer thinner and those paper towels.  If a towel is in my hand any longer than 30 seconds, it is dirty.  Grab another.  Wipe and rewipe until the surface is perfectly clean.  Go back over all the trouble spots like the fenderlip, bumper areas, sills, jambs, ect.  I do not use PrepSol or any other wipe compound, just lacquer.  I do not need Fisheye Remover in the paint.  I just have a very clean car! 
That covers the prep.  Wipe the car with a tack rag, and spray the sealer.  Sealer is a quick drying coating that is very close to the color you are painting.  Many basecoats are transparent.  You will waste basecoat trying to get hiding coverage.  The sealer is cheap compared to the basecoat cost.  After the sealer dries, tack rag again and apply the basecoat.  The clear goes on after, according to the instructions 

Color sanding and buffing.  After the car comes out of the booth and you find your trademark (mine is an eyelash in the top coat of clear and usually a run near the door handle), let it sit for a few days.  Grab some 1000 grit on a 5" board and start wetsanding out the runs.  A slight blast of contrasting color of paint over the run will act a as a guidecoat.  It is very hard to see a run in the clear when you sand it to a dull sheen.  The guidecoat makes it show up clearly.  Anyway, sand out the runs, gradually working up to 1500 grit abrasive.  Then you need to buff the flat paint out into a high gloss.  I use a Milwaukee buffer and Presta compounds.  There are dozens of buffers and hundreds of compounds.  Presta is very cheap and works fantastic.  Use what your mentor or paint store suggests 
 
Copyright 1997 Scott Bruning 


 
 

 
Painting the vinyl and plastic in a Z is easy.  There are 2 sources for the dye.  If you don't have a paint gun, find SEM vinyl dye at a good paint store.  SEM is the only way to go, and I have never found another product that works as well or lasts so long.  It also looks totally natural.  They have Satin Black for your 240Z, and Napa Red for your red 240Z.  They have ZX colors, too. Please do not even consider any other brand.  Been there, done that.  In my experience, there is no other brand that has the correct gloss, durability, and chemical composition to bond to the vinyl.  SEM is about $7/can.  I use 4-6 for an entire interior on a 240Z.  If you have a paint gun (door jamb gun is good, HVLP jamb gun even 
better). Dupont has vinyl dye that is comperable to SEM.  It is about  $20/quart.  Does one car. 

Preparation is everything! Here's my process: 
1.  Remove seats and carpet 
2.  Use a couple of rolls  of paper towels to clean all the vinyl/plastic (VP) with a water based cleaner (soap/water, ammonia, Mr Clean, Mrs Pineoil, ect).  Let dry 
3.  Wet wipe the surfaces with lacquer thinner.  Not Enamel or poly thinner, just cheap lacquer thinner.  Wipe and scrub and scrub.  You will notice the VP getting soft.  Stop before you ruin the grain pattern. 
4.  Now shake your paint can. If using the Dupont, it is ready to spray.  Mask off all the unpaint items.  I use Big Gulp bottoms taped to the gauges. 
5.  Rewipe the surfaces quickly with a very wet paper towel, and start fogging on the dye.  It is very thin.  You may end up with 5-12 coats to 
get good heavy coverage.  Let dry, and you are done. 

Note:  DO NOT PAINT THE SEATS.  IT WILL RUBv OFF EVENTUALLY ON YOUR 501'S. 

The Napa red is a precise match for the Datsun red interior.  Even a patch of paint will blend in to the existing panel. 

The theory behind the lacquer is that it chemically softens the VP.  When you apply the dye, it soaks in and grabs the substrate. 

Dupont also has texture paint to redue the texture for Ford Bronco tops.  It so happens to look like vinyl when it is dry.  I use it to redue the sill plates... It also works for roll bars to spiff them up.  The stuff is bulletproof when dry.  It does not match the Datsun sillplate vinyl exactally, but it is a lot easier than trying to recover that rusty piece with contact cement and vinyl.  This paint has to be applied with a non-HVLP gun (your normal old fashioned gun is not HVLP).  It's the pressure that makes the spiderwebs as it comes out, 
which then coagulate into the vinyl texture.  This coating can then be recoated with black semi-gloss vinyl dye. 
 

Bare metal prep 101: 
 
 The best metal prep for the average do-it yourselfer on bare metal is an epoxy primer.  I use PPG DP series.  DP40 is black.  It gets mixed with 
a catalyst (DP401 or DP402).   They say if you don't sand it within 7 days...don't bother.  It gets very hard.  It is applied with a paint gun. 
All modern paints with a catalyst have isocraynics in the cat.  Use a respirator! 

The epoxies do a great job of sealing off all the substrates.  Modern paints are very hot and agressive.  If applied over a old lacquer or 
enamel job, it will likely cause the old stuff to bleed through.   Smother the car in epoxy, then start the bodywork.  Put more epoxy over the filler, then apply some K200 and K201 catalyzed primer.  This stuff goes on thick, but sands wet sands like butter.  The best way to wet sand is to apply a mist of black lacquer over the unsanded K200, then wetsand with 400 grit.  The low spots will show up 
as black.  Reapply filler, and do it over again.  Good luck.