I use the cotton pads(the balls are too messy) to clean up the worst of it. Just put a little rubbing alcohol on the pads and get what you can. Then I use q-tips with rubbing alcohol to finish it up. Doing this has always worked great for me.
Use Isopropyl Alcohol to clean the top of the cpu. You can find it at Wal-mart in the medical department where you would find band-aids, neosporin, and the like. Try to get the 90%+ one instead of the 70+ one. You'll also need the lint free cloth. The ones used to clean glasses lenses work well. You can probably get one from 20/20 eyeworld or something hehe. I never did look for one at Wal-mart but you may find one their if you ask one of the roaming salespeople.
When I"m trying to get old AC3 off I use a Q-tip with Goof Off on it. Wipe it clean after that with some cotton pads, then clean it really well with Isopropyl Alcohol. Then I dry it off with a coffee filter.
Isopropyl (rubbing) alcohol and Q-Tips here too. I clean the bulk of the AS3 off with a couple of dry Q-Tips, and then use one dipped in the alcohol to get what's left. (and then another dry one to dry the chip off when done.)
Done this way...a 300 count box of Q-Tips will last you a loooong time, even with fairly frequent CPU swaps/upgrades, and a $.99 bottle of rubbing alcohol will last you the remainder of your natural born life.....
What about somthing like engine starting fluid... the stuff you might spray into the carb... it melted AS3 off my heatsink before lapping because it has alot of ether in it... evaporates in seconds... but im not sure how it would affect the CPU. Any ideas?