I did one last year that turned out great. I skinned it first, took the eyes out and lower jaw and tongue off. Then I bought a big pot and simmered (not boiled) it over a camping stove. Simmer in water and borax 20 mule team (to cut grease) for about 15 minutes, pull out and scrape and pick junk off. Do this over and over and over again until it is as clean as you can get it. Us a piece of wire like a coat hanger to dig up in the brain cavity to get all that out. Once I had it as clean as possible, I took it to the car wash and power washed it, an amazing amount of junk came out when doing that. Remember, any flesh left on it will rot and smell funky. After I had it clean, I let it dry then covered it with a mixture of 40 volume peroxide and bright white (hair products for bleaching hair). Make a paste out of that stuff and cover every part of the skull with the paste. Once the skull is covered with the paste, cover it with saran wrap and put in front of a space heater and rotate. The heat will activate the bleach. Get it as hot as you can without burning the saran wrap. I would heat it for at least an hour, more if you can. Unwrap it, wash it off and walah, a great looking skull. Good luck!