I used VHT paint. It held up good for a while but then started rusting again. I think it was because I didn't bake the paint like the can instructed to but i thought that the on and off of the engine heat alone would bake it. Guess I was wrong.
If they are VERY clean, and you can get them hot soon enough it lasts fairly well. I've shot some right on the car (messy) so I could get the temp up right away. An oven is better, but finding one large enough can be a problem.
Eastwood makes some brush on paint that I had very good luck with. Sandblast and wipe down with laquer thinner. The paint is very thin, like water. After you wipe with laquer thinner, don't get finger prints on them or you have to do it again. I used black on mine and they lasted 3 years til I sold the car.