That isn't a good idea because of all the lint from the paper towel. I would use rubbing alcohol and put on a latex or rubber glove to scrub off the leftover thermal stuff that's on the CPU. We have those in our medicine cabinet, lol. Used for cuts and to clean CPU, lol.
Oh, try this too. Wrap your hands in a sandwich bag or leftover antistatic bag from hardware you purchased before to do it. Don't use your fingers directly because of the oil on it.