There are various sprays and bake ons available, I don't have any sources for them but it should be a simple matter to find one, they're used alot in restoration of old tools and auto parts and such. The easiest bet is to go to the auto parts store and look for black crinkle valve cover spray paint(the one I have says it's for corvette valve covers), and follow the instructions on the can to the letter. It'll take a good while to cure (think a week or so) to full hardness, but should be just the thing to experiment on without having to resort to ordering.