[Logan]

If you're going to paint direct to metal, the metal needs to be sand blasted or completely clean. There's no point in spraying over old paint or rust. Por 15 is probably one the hardest most durable paints out there, and if you spray it on good clean metal it'll probably be the last time you have to spray it. For me, I like spraying primer on my chassis peices. I can sand it and reprime a few times to get the pits out of the metal. I like my frame rails, backing plates, and axle assembly's to be as slick as you can get them. I even used a little bit of filler on my speedster chassis since it shows. Either way if you do it right, you should have good results.