I've never painted an entire car, but my father-in-law and I painted the camper shell on my truck last summer. Since my father in law does a lot of paint and body work (and I'd never done any and wanted to learn), we decided it'd be a good small-ish project to tackle ourselves. I'll run through the basic process we followed. I'd written this post to provide info in my build thread for those interested in painting with a base coat + clear coat, but I figured this would be a good place to post it as well.
The original silver silver paint was in really good shape, which allowed us to do a basic 'scuff-and-shoot' rather than completely removing the old paint. The main problem with was that the bottom edges of the shell were pretty beat up along both sides where it had been sitting on a garage floor. Thankfully there were no cracks or other significant damage to the fiberglass, which would've added a bunch more work.
There are several variants of the 040 Toyota Super White color in the paint line we chose. The paint shop gave us paint cards to compare to the paint on my truck to see which one is the closest match (my truck ended up being a slightly more bluish hue than the official 040 white). If the truck was brand new, this wouldn't have been an issue, but since the truck was almost 5 years old at this point, the paint had definitely faded from summers in Texas.
All in all, this project took 2 full weekends of work to finish, and that doesn't count the time reassembling the Yakima tracks on the roof and remounting the 3rd brake light in the back. It was a real eye-opener as to the amount of work that goes into a good paint job. And believe me, this is definitely no show-car quality finish, we could've spent twice as much time filling/sanding/filling/sanding/etc if we wanted to. It was a ton of work, and if I had it all to do again, I honestly don't know if I would do it myself or just take it to a body shop (or better yet just wait to find a camper shell that's the correct color...seriously). I definitely learned one thing - I don't have the patience for paint and body work. All in all, I have around $400-500 in materials alone if you count all the miscellaneous items like tack rags, degreaser, tape, etc etc....whereas a body shop could've probably done the whole thing for around that much. However, I don't think a body shop would've done all the steps that we did, so I don't think the end result would've been as good in terms of the longevity of the paint job.
Materials Used
Primer: Nason 421-19 gray w/ 483-87 Activator
Sealer: Nason 422-51 white w/ 483-87 Activator
Color Coat: PPG Deltron DBC in 040 Toyota Super White variant 'B'
Clear: Advantage 545 w/ Activator
Fiberglass Filler: Dynatron Dyna-Glass short-strand fiberglass filler & activator
Polish: 3M Finesse II
Glaze: 3M Finishing Glaze
Miscellaneous: Nason silicon wax remover (SWR); 80-, 120-, 220-, 400-, 800-, and 1000-grit sandpapers; tack rags; lacquer thinner; etc etc
1. Completely disassemble camper shell - remove the side window trim and windows/gaskets; completely remove rear window/frame/gasket/lift-glass by drilling out rivets; peel/scrape off the old bulb seal material from the underside of the shell (the area that seals to the top of the bed); remove roof rack tracks, gaskets, and hardware
2. Tape/mask off all areas that you don't want to get paint on (i.e. the entire interior of the shell since you do NOT want to remove the carpet, huge PITA)
3. Wipe the entire surface down with silicon wax remover
4. Sand the existing paint with 400-grit sandpaper on a DA sander. This gives the primer something to 'bite' on. Blow/wipe camper surface and surface of sandpaper frequently while sanding; this helps to prevent build-up of excessive sanding debris between sandpaper and surface which causes excessive scratching.
5. Use spotting glaze to fill in small (i.e. pinhole-sized) holes/divots in surface. After they're dry, lightly sand them with 220-grit sandpaper, followed with 400-grit paper.
6. Use 80-grit to rough up the surface of the damaged areas on the bottom lip of the shell. This will give the fiberglass filler something to bite on.
7. Use Dyna-Glass fiberglass filler to build up damaged surfaces on bottom lip of shell. Sand these surfaces down with 120-grit sandpaper on a foam sanding block. Blow/wipe surface frequently during sanding. Reapply fiberglass filler and resand as many times as needed to get a smooth surface. Ensure that all surfaces match the contour of the shell.
8. Use standard body filler to fill low areas as needed. After filler is dry, sand with 120-grit sandpaper on a foam sanding block. Reapply body filler and resand as many times as necessary to get a smooth surface. Blow/wipe surface frequently during sanding.
9. Resand entire surface with 400-grit paper on foam sanding block. Blow/wipe surface frequently during sanding. Check for problem areas and repeat sanding as needed.
10. Wipe entire surface with SWR.
11. Check tape to make sure it's still sticking properly. Replace as necessary.
12. Wipe air hose (for paint gun) down with SWR. Wash floor of work area with water hose and leave floor wet. Wipe surface of shell with a tack rag to pick up any remaining lint/debris.
13. Mix primer according to specs on bottle. Add fisheye preventor to primer.
14. Shoot primer over entire surface and allow to completely dry.
15. Sand entire shell with 400-grit paper on a foam pad. Blow/wipe surface frequently during sanding.
16. Wipe surface with SWR. Re-spray primer on any low areas. Resand. Blow/wipe surface frequently during sanding.
17. Wipe surface with SWR.
18. Shoot sealer coat (this step is optional. I did this mainly because the primer was gray and we chose a white sealer, meaning the paint would end up coming out closer to it's ideal color when shot over a white base instead of a gray base).
19. Lightly sand seal coat with 400-grit paper if necessary to remove nubbins. Blow/wipe surface frequently during sanding.
20. Remove all old masking tape and paper. Re-mask and re-tape all areas with fresh paper/tape.
21. Wipe surface with SWR.
22. Wash down floor of work area with water hose.
23. Wipe surface of shell with tack rag.
24. Mix paint according to specs on bottle. Add fisheye preventor.
25. Shoot white paint onto camper surface. Make sure to shoot with even overlaps. Shoot enough paint on each area to get surface fully 'wet' but not enough to cause a run. We used 2 quarts of reduced paint for the entire exterior of the shell.
26. Wait 20-30 minutes for paint to flash dry.
27. Mix clear according to specs on bottle. Add fisheye preventor.
28. Shoot clear onto surface following same procedure as white paint. We put a TON of clear on the shell 1) because we had a bunch of it, and 2) so that there is plenty of clear available for sanding, both now and in the future.
29. Allow paint to bake in the sun as long as possible (we left it out for most of the afternoon)
30. Wait until next day to wet-sand the clear coat. Wet sand entire surface with 1,000-grit on a soft foam pad, keeping the surface very wet and rinsing often with clean water.
31. Polish surface with 3M Finesse II on a circular polisher to remove wet-sanding marks.
32. Apply 3M Finishing Glaze to surface with a circular polisher.
33. Reassemble windows and roof rack hardware VERY delicately (especially when the paint has only been curing for about 24 hours and you have to remount the shell and get on the road for a 4-hour trip back home).
34. Wait at least 3 weeks before going through the car wash / power washing / etc. To give you an idea of how soft the fresh paint is, after a week of this thing baking in the Texas summer heat, when I remounted the 3rd brake light, just the pressure from pushing it down onto the surface of the shell to get the sealer/adhesive in place caused the paint to displace around the brake light housing...that one had me puckered up for sure. Thankfully it hasn't started peeling or chipping away yet...fingers crossed.
Oh and I forgot to mention the whole process of sanding down all of the metal parts of the window frames, taping off the glass, degreasing the frames, and painting all of them flattened black (my father-in-law happened to have a quart of Lexus gloss black paint on hand from an old repair so we just added some flattening agent and shot it). They came out looking great.