The best/cheapest way I have found, if you have a place to do this and the time to do it, is to let the skull rot in a bucket of water. The bacteria in the water will completely clean the skull. Fill the bucket up to the sheaths and let it sit in the sun. The sheaths will come off after about a week in typical early fall temps. Clean these out and fill with borax upside-down for a week or two. Then fill the bucket over the entire skull and cover. Periodically check the water level and add water when necessary. I cover the bucket with rocks to keep the critters from tipping it over. Where I live, it generally gets cold before the skull is done soaking, so most of mine seem to get done around mid-spring of the following year. About a 6-month turn-around. When the skull is mostly clean, dump out the water, being carefull to not loose any teeth, as they will be loose, as will some of the joints in the skull. After you hose off the skull and scrap what little remains, let it dry and then super glue teeth and joints together. The skulls come out with 0 scrap marks, and with a nice natural color . . . The key is having somewhere this can be done.
