I use rustoleum, various versions, for engine block, small parts, e.g. alternator bracket, suspension etc. and it works fine and chemicals haven't seemed to be a problem.

Urethane, 1 or 2 part, has a better gloss for sure.

If I had all my small parts ready and could paint them all at once, it might make sense to mix up catalyzed paint. But to cover/protect something as you go, rattle can!