Yeah, my father and I did the same to a few bucks this past year as well. I've tried countless ways to do it from chemicals to boiling. I found the easiest was actually the most straight forward. I simpley cut off what I could with a knife, scored the remaining meat and sinew that was left on the skull and then simply powerwashed it ! After it was clean a little soaking in hydrogen peroxide and it was done.
It was actually easier than most times I have boiled off a simple skull plate.