On chrome plastic, the best way we have found is to use a 00 or 000 steel wool for the initial removal (wear a glove....keeps your fingers from turning gray), followed up by a 0000 to smooth it out......scratches and imperfections can be worked on with a wet-400 grit prior to the steel wool.
The steel wool gets into small areas and creases found in most molded trim such as dashes and the like, and safely removes the chrome...usually pretty fast as well.
Do NOT use a self-etching primer on the plastic.......a good high-solids lacquer (fast dry) is best..... look for Dupli-Color brand in your auto parts store.....excellent quality.
Good luck..........................
