First post and new member ftw!
FYI, I sold mine on the bay. Black 3G jailbroken 3.1.2 and it went for $202.50. As for your question, grab a bottle of meguiars plasti-x plastic polish and a buffing foam pad and go to work. An orbital buffer will work best and I've gotten "brand new" results myself using this process. This also works on the metal band.