A few things:

1. I am a real believer in 2-part epoxy primer/sealer. It takes a little time to dry but once it does, bleed-through problems are OVER. Also, it's very good on bare metal. I got this rather expensive crap in a spray can from a body shop supplier that was supposed to be a sealer. No, it wasn't.

2. don't think extra energy (heat, UV, or both) is a good idea on 2-part paints. If painted at proper range of temperature, it will "dry" (solvents gone) in maybe an hour, and harden from the chemical reaction which is designed to take place optimally at the the proper temperature. I would worry about vaporizing the solvents on top of the paint while the underneath is still "wet" (i.e., orange peel). I've found that a slightly warmer car and cooler paint/atmosphere works really well, which seems to dry the paint from the inside out. I touched up my car this weekend and other than blending issues (it takes real experience to blend a spot, experience that I don't have), everything went on like spraying on liquid glass, which is a rare treat.

Epoxy primer sealer eh?
 

Thanks for the epoxy primer sealer tip - I'll try and find some and give it a go. My most recent experience of epoxy made products has been good. I've discovered Nu Metal (made by KBS). It is amazing stuff - it will stick to most things and does indeed dry as hard as metal. I doubt it is as strong as metal though so DON'T USE IT ON STRUCTURAL PARTS OF YOUR CAR!!!

When doing full restorations from bare metal, epoxy primers are/were a good option for durability, particularly if the car had rust to begin with. I personally have no experience with them, but high end builders would specify that as a base coat.

At an absolute minimum, a self-etching primer is required on bare metal, once any body work and bondo filling has been done. Then follow with high-build primers, then sealer, color coat, clear coat.

If the original paint is solid and and has lost its gloss or light degredation on the surface layers, or if you are just changing color, then it can be sanded with 500 and shoot over it, no primers required.

Nice one
 

Ah ha I'm glad to read that you agree with Wheeler Dealers - that's also one of their top tips...

...they are often quite entertaining programs that can be watched whilst your wife is hogging the TV watching some hospital soap.

See

http://www.youtube.com/watch?v=tSiYDSPCIGE

For example

Whew! An avalanch of info but a little too late for me.

Thanks guys!

Ditzler DP-40 from PPG was the premier primer surfacer for years. Though never use it as a topcoat. The bisphenol-A epoxy has no UV durability. You always need to topcoat it.

I know that PPG has dropped the Ditzler name, but there are still DP primer surfacers on their website. They are very good.