If it is a rubbery or waxy thermal pad, I start scraping most off with a plastic tool (so as not to scratch the HS or CPU), followed with lighter fluid (naphtha) to remove the remainder, follow with high-proof alcohol (ethyl or isopropyl) to remove any lighter fluid residue and enhance drying and dry (coffee filter - lint free). If it's your typical grease like AS or Ceramique, I just use one or two passes of high-proof alcohol and dry.
.bh.