TahoeTom made a lot of good points there on Epoxy Primer. I also am on Autobodystore.com in the forums. Name there is Junk also. Very good forum for autobody stuff. Also they have good pricing on autobody tools. He also sells materials, but I buy those local.
I myself have been having excellent results with Autobody masters Epoxy Primer 8411. You can use it as a Epoxy primer or sealer. I think of Epoxy primers as a glue. They glue the next coats of material to the base surface. Epoxy is good for moisture resistance. Epoxy doesn't seem to sand well. Most of the guys put Epoxy primer on and then during the recoat window will spray a Urethane Primer surfacer over that. Then you do your block sanding in the Urethane Primer surfacer. For Urethane Primer Surfacer I've been using Autobody mater 8443. I like the Autobody Master stuff as it has been a good value for me. The higher end products by PPG and Dupont may work better, but I've never felt these work poor. Autobody Masters stuff is also sold by Oreilly's under another brand. All the numbers match up though.
Now when it comes to paint color match and coverage I'm definitely a believer the better paints cover better and match better. PPG's cheaper Omni line I've used and found it didn't cover well and the paint match could be bad. Now on an overall paint job and in the right color it can be fine. PPG's DBC and DBU are higher end lines and work great. one's newer than the other, but I've used both. Dupont's cheaper nason line of paints I've really liked. I thought they covered well and were reasonably priced. I'm doing my crewcab paint in those. Dupon'ts higher end Chromabase paint is nice and i've shot a little of it. Some guys talk about it having coverage issues.
Clear coat. I use Dupont's nason clear coat. Goes on really nice for me and is reasonably priced. I've tried higher end clears and felt they did no better for me. Now there could be a longevity concern, but my daily driver I used this on 3 years ago is still fine.
Thanks,
Jeremy