I took a Mule deer on my 30Th B-day I made it into Pope and Young record book, Boiled the skull same thing. Brain soup EMMMMMM Not.
I have a couple of taxidermy friends that said, 2 things. 1 way is to hang it and let the fly's ley their eggs in it let the larvy eat at it and pick it clean. But if you live in rural area that will piss off every one because of the smell. 2 nd, Bury the skull in loosend soil or a compost pile and let the worms do the rest. Just check it every now and then, if you can stomach the smell!!
I hope this helps!!