Is it just thermal grease or is there anything else on there? I found that the best method for cleaning thermal grease, is getting some cotton pads(not balls, they're too measy) and wetting them with some rubbing alcohol(just cover the opening of the bottle with the pad, flip it upside down and back and you it should be as wet as it needs to be). I use that to clean up my main mess, then I use the q-tips to finish up the little patches and stuff that are hard to get to. Sometimes, part of the fabrication will be slightly staind and it won't come off, this is fine, just make sure that there's none left on the chip or any of the bridges before your done. Make sure it's dry, and you're done!