I use a paint to do stuff like that. It comes in a spray can ans it is made by a company called SEM. here are several kinds to use such as "trim black" or satin black, but the trim black is designed for the elements. It's kind of pricey..about 15 bucks per can but it looks very good when it drys. Be sure to use dust coats, dont try and make it look shiny, it will dry flat.