epoxy primer
 

Ok, first I've never painted a car before until my Porsche (I couldn't have been smart and stared on something like a Yugo:D - noooooo, I had to make a Porsche me first try)

Anyway, I only painted the left q-panel, bumper and lower valence. Came out good. Im in the process of color sanding - very un-nerving to say the least. When I'm done with that I will be prepping the rest of the car in for the rest of the color and clear I will be putting on top of the old single stage. There are a couple of spots where I will need to go down to bare metal and respray with some kind of primer.

My question is, if I am not taking the whole panel down to bare metal, but just a few square inches, what type of primer should I use on this spot. Do they seal a epoxy primer in a rattle can. Or should I just scuff the whole panel and expoy primer over the older single sage and reshoot the new base/clear on top of that?

I would just primer the spots you go to bare metal. Put about four coats of primer and then sand flush with the factory paint. Then paint base and clear. I am not an expert. But the owner of the body shop I used to restore my 69 is one. He always used the factory paint when possible as a primer (of course he sanded it like a primer before the base coat). My car had about half sanded to bare metal and then epoxy primed and half using the factory paint as primer. Depends on condition of old factory paint. Good luck. This is a job I would rather pay for. To wet sand the car by hand about three times then polish it is too much work for me. Good Luck.

STOP.
You are all spun around. Bare metal needs an acid etch ...rattle can primer. I would sand down the rest of the panel and use acid on the spots and 2x primer on the rest of the panel.... over the patches too.
Wetsand the 2x epoxy.
....or , forget the 2x primer and use a 2x sealer... with no sanding after... just go ahead and spray the base & clear coats.
I would go 100% bare metal, 2x primer, sand 2x sealer, 2 coats base, 2 coats clear, wetsand 1500 & buff with wool pad and medium cut 3M microfinishing compound, finish with foam pad & 3M imperial glaze.
.... drive its balls off.

Unless you are going to full bare metal It would be better to spray some etch primer on the bere metal spots. Then some high build to blend into existing paint. Then shoot the whole car in epoxy over the factory paint which has been scuffed back. This will seal the surface and give a consistant stable base for the new paint. If you don't have the same base for all color and clear you risk the paint lifting or have a color mismatch on the car.

YMMV

I can just use self etching primer from a rattle can like the kind I find at Autozone or the like and rattle can high build primer. Then apply a sealer or or do I use an epoxy primer over the entire panel (including the existing paint)? That part I am still confused on.

The epoxy becomes your sealer and base. I don't know if I would trust rattle can high build primer to last. I would use a two part system with high solids content and quality resins. They will stick better, last longer and be easier to sand.

Nothing from Autozone. The acid etch rattle can spray primer will be found at a real auto paint store..... and actually say " ACID ETCH" on the can. You lightly spray the bare spots to let the acid bite into the bare metal. If the panel is then perfect.... you can go right to 2-part sealer.... it has a hardner and reducer added to the base sealer .
If you need to fill in imperfections, use the 2 part primer, wetsand then shoot base right over it.

Doesn't the acid etch primer attack the paint around the bare spot? I know it can attack fresh primer.

primers
 

my humble experiences painting on VW's:

midlife--yes in my experience (dupont variprime) acid etch can (did) attack surrounding paint

i started using exclusively PPG DP40LF 2-part epoxy primer/sealer, no problem on prepped bare metal, a little hard to shoot (can pebble if too warm or not enough pressure). epoxy is hard, doesn't like to be sanded, but be sure to let it dry completely before any sanding or else the scuffs will continue to open up as it continues to dry and shrink.

Next I used PPG K36 acrylic urethane primer surfacer which is a sandable hi-build primer that sprays on thicker and can even-out any MINOR imperfections in the sealer. when dry, mist with a "guide coat" then wet sand.

I used PPG Delstar 3-part acrylic enamel for topcoat, urethane maybe easier to work with but more expensive also.

just my 2 cents.

No, my body guy turned me onto the rattle can self etching primer, purchased at a real autobody paint store, when I did my roll bar. I had to sand down to bare metal in a few spots but the rest was the p/o's paint. Worked great as a base for my finish coat.

So do I then apply primer over the whole panel, or just over the epoxied area. Or is the epoxy my primer in this case?

I agree, stay away from rattle cans.

In PPG terms, you can use epoxy primer to mixed as a sealer to cover the old paint system and bare metal. (DPLF epoxy) You will need to prep the old paint surface by sanding. This will provide tooth for the epoxy to form a mechanical bond to the old surface. The DPLF will have a window of time where you can shoot a compatible paint and form a chemical bond to the epoxy.

Also, Acid etch and self etching primers are only used in some brands of paint. Not in PPG.

Ok redcoupe86
I have done a lot of bodywork and i never used rattle cans !!!
Sand it down to bare metal with 80 or something like this !!
but before you put primer on this spots sand it with 240 that you can't see any scratches from the 80 sandpaper otherwise you will see scratches after the paint is completly dry !! Usually after 6 month's depens on the inviroment !!
i always use the primer from Sikkens they call it 940 and mix it 2:1 with the hardener !! Then put on 1-3 coats !! It also depens if you use bodyfiller or you just have nice clean bare metal !! and if you tape the car ,lift up the edge's around the spot !! And standox has some good clear!!
let it dry good (i guess you don't have special heater )
Good luck