I'm not sure if one reacts better over powdercoat or not, but I have used 2 different options from a rattle can. Clear enamel and clear lacquer. Clear enamel is a bit more finicky (in my experience) to apply nicely, but will shine when dry. Lacquer is a bit easier to work with (in my opinion), but will be dull when it dries. You will need to polish it with rubbing compound and progressively-lighter grades of polish until you get the shine you want. I never had any luck with polishing enamel. It's a lot more work, but I think the result is superior with lacquer.
Edit: In my examples, both types were intended for automotive applications, for whatever that's worth.