Motorola Droid X :: Anything To Remove Grime From Phone/

I was using a silicon case until recently, i removed the case and the lower back end of the phone where the speaker and mic is that was an opening on the case. well, i thought that the ring around those 2 things was just dust build up but now i can't seem to remove the ring that it formed. wondering what i could use without hurting the paint. i wish i could show pictures, but i don't have any. the case was this: where the bottom part of is opened.