I knock off all molding lines and flash with files, sandpapers, Xacto, whatever, then block-sand the high spots such as around door lines, and then I go at it with either nail polishing sticks or Wright's Silver Cream or both. It's not terribly different from polishing paint. In fact, you can go a little harder, as you never have to worry about "burning through." (This does NOT mean that you're okay to use power tools for the job.)