D.K.
I would say that you could try dish soap if you're very careful not to get it on his face. Dish soap is specifically designed to combat grease of all kinds. I would recommend the Dawn Direct Foam, it'll cut through the worst grease. Again, just be very careful not to get it on his face or in his eyes. One of my ex-BF's tried this when his daughter got into the vapo-rub when she was visiting him and it worked.