A fast way is to boil the skull. After boiling the brain will fall apart by inserting a long smaller blade knife into the brain through the back of the skull where there is a opening to the brain, use the knife to break up and cut up the brain while it is still inside the skull. Once you have it broken up you can turn the skull over and shake the pieces of the brain out of the hole. I also return it to the water and cook some more it helps to get the pieces floating out of the skull.Keep the antlers out of the boiling water or you may end up with some antler damage. When I bury them I dig them up close to a year later and all of the brain is gone. You can also check into the beetles that you may have a taxidermist that can do this for you.