Just make sure its free of all dirt and grease before you paint it. You could also rhino line it. But what ever you do, it needs to be clean. Surface rust will cause the paint to lift off and spread. If you have the funds, have it blasted. You can put high dollar paint on a crappy prep job and its going to look crappy. You can put cheap paint on a well prepped part and it will look good and last longer. The beauty is in the prep, then the paint.