Take a clean rag, soak it down pretty good with isopropyl alcohol. lightly rub handle, and allow alcohol to penetrate cork. Let sit for 30 seconds, and then apply/soak rag again with alcohol. Then, wrap rag around handle and twist handle, or srub the residue off. Alcohol will loosen all imbedded sweat and dirt. Makes handles soft again also. Best rememdy I have found to date, but I am sure there are others.
Don