grundy, I'd let it soak in Dawn dish soap and water for at least 3 weeks. It will help remove any little flesh that might still be clinging. Make sure to add a submersible fish tank heater in with the soap water and skull.
After 3 weeks rinse the skull and than let it soak in clean water 24 hours. Rinse again and let it set out for a week and check for grease. If there is still grease put it back in the soap solution with the heater. Or you can put in acetone for a couple weeks. Keep the antlers out of the acetone as much as you can. the areas that will develop the most grease are the back of the head and the fore head.
As for whitening. You can use the 40 volume hair developer from a beauty supply store. Just paint it on getting it up inside the skull and brain cavity and wrap it in plastic wrap for 24 hours. Rinse it and let it dry. If it is not white enough paint the developer on again and do another 24 hours. After that it should be white.
