No need to wait that long using acetone. A few days will dissolve ALL grease, oil and fat. The skull will remain white and never yellow. It is a little tricky to seal off the acetone when dealing with antlers and prevent evaporation. Just be creative since the acetone will not harm the antlers. For a bear skull, just cover the skull with acetone and put a bucket lid on. You can keep reusing the acetone. It is pretty cheap at big box stores in gallon cans.
