I got a used racquet today and it is in great shape as far as scratches (just a few at the top but that appears to be black plastic). Very small nick on the paint, and other than that, very eye clean. But the grip is white (Head absorb something or other), and has that black staining from when the racquet is gripped. Would like to restore the whiteness to it. Suggestions on what to do, and more importantly, what not to do?