As I painted cars for almost 35 years, if you're just prepping it for a topcoat, then sand it with 320 grit and a circular sander, air or electric. If you go through to any metal, that will need to be etched and primed ! Try to use a two part paint if it's a solid color. Paint with a hardener and reducer ! Try PPG ! Good paint. Hope you have a proper spray gun and respirator !