I'm very experienced with body work and paint work, but my experience is dated. I was taught with laquer primer that could be used to fill the sanding scratches with block sanding and re-primering. But ... things have changed. I wonder if someone could guide me as to the the type of primer I'll need to cover body work, in what grit the bondo is left before primering, and how to sand primer/paint before spraying paint.

I have a tailgate, used, that is currently black. I have purchased Summit acrylic urethane white, to spray it. One side of the tg is nearly all bare rusty metal. I'll be doing the body work myself, and the spraying. Thanks in advance.

 

Your local body shop supply company should be able to point you in the right direction and relate it to the products you are already acquainted with. As far as what grit to use it is like riding a bike, nothing has changed.

 

I also sprayed lacquer paints,lacquer clears, eventually following the paint industry progression from single stage paints to base coat clear coats and every possible magical additive or product in between.
For a long lived repair on your tailgate I would sand the bondo/plastic filler with 80 Grit to rough it in.More filler where needed, 80 again,, finish with 180 before 2 stage,epoxy primer( primer with a hardner), block 1st primer coats with 180,prime again (or again &again),final block with 320-400. If the finish is what you want at this point ,I use a "sealer",then the acrylic enamel you bought.
The old lacquer primers were the weakest link in a paint job.Epoxy primers have very good adhesion properties. The sealer (yup,I use 2 stage sealers) is a barrier coat between the primer and color coat preventing sand scratches,body work etc eventually showing.
2 or 3 things come to mind. 1) you generally will get a zillion different opinions on "what grit works, what doesn't"." This product works better", "my buddy had a bad experience with that" type advice.I am stating a GENERAL sequence in regards to your question.
2)If you go to a paint supply store they will sell you 1qt. primer $100,1 pt.catalyst/hardner $90, 1qt.sealer $80-90,1 pt. hardner $75...........see where this is all going? Just doing a single tailgate here !! So,painting the 100% proper ,fail proof way ,cost big bucks.!
3) If the tailgate is all you are doing;just for yourself, my thoughts are; Spray can or 2 of primer,do the bodywork 'til happy,final coat of the primer sanded w/320-400 before painting. Let it dry for a few days to let all solvents out. Shoot your acrylic enamel. Let that dry for a week or so sand & buff any imperfections.Did a lot of 'em years ago like that;it might be what you need. good luck

 

Other than epoxy primers not much has changed on prep. and the epoxy isn't what you want for sanding it sucks for that, it's more of a base sealer and adhesion coat.

 

- I agree with Rat2 and 440 above
- I do a lot of custom painting , I airbrush, I do body work, prep, paint and clear. I even wet sand clear and buff. I have the modern stuff on hand So here is the way I do it.
- brand names vary to personal preference and location. not promoting anything just fyi, for primers and clears I use mostly SPI (southern poly urethanes inc.) and some PPG (expensive), Sherwin Williams (convenience when I run out of SPI)

Start with sanding as best you can all the old stuff off or sandblasting the tailgate, wipe with w/g remover then put on "EPOXY Primer", this stuff by SPI that I use is great, it sticks to the bare metal and locks down any remaining rust or old paint left in nilks and crannies. then do your bodywork on top of the Epoxy Primer, it adheres to it great, no sanding of the primer needed (within a certain time limit). after your body filler is sanded out, spray "2K Primer", this is your sanding primer, you can sand this wet or dry and repeat if needed. after the 2K Primer is sanded I mix up Epoxy Primer as a "sealer" (reduce it down) and spray over the 2K. your body supply may recommend a different sealer, but I like the epoxy mixed as a sealer. your now ready for your paint & clear

 

Try some polyester glazing putty to fill sanding scratches. It is sort of like very thin bondo. It comes in a metal tub, you need to add hardener for it to cure. I find a rubber applicator works better than a plastic one for this material.

I wet sand it with 220, follow with a 2K primer. More sanding, more priming, until straight.

 

I just finished my truck and I used laquer primer, none of that 2K stuff as I was doing 1 panel at a time and the 2K just does not cut it in my book as user friendly.
What you don't use you have to throw out because of the hardener.

On Bondo I took it down first with 80 grit then 120 and a final of 220, this took care of most sanding marks before primer.
I then put on 3 or 4 heavy coats of primer on the panel. I would then wet sand with 400 to knock down the ruff primer and a final sanding with 600 wet before painting.
Paint label was either 400 or 600, I felt the 600 was the better way to go and happy I did.

I painted the truck in single stage enamel with hardener, It was the bottom line that the paint store carries because of the $$. I have about $1000 just in the red paint for my truck not counting primer, white paint or thinners. Because of the final sanding with 600 the paint flowed out like glass and I am really happy with it.
I was not going for a show truck paint job or I would not had painted it in my garage and maybe gone with 2 stage paint.
The truck is a vary good looking driver and I am happy with it. If someone has something to say about it I want to see their paint job done in their garage not a paint booth.
No cutting or buffing of the paint on this truck and it is a little dirty as I drove it in the rain a few times.

Dave ----