Boiling & Simmering flat out SUCK and you can ruin a skull quick doing it!

Boiling can and will cause bone to break done especially with some of the chemical I've heard some people say they put in the watter. It can also cause grease to set into the bone and cause discoloration
Maceration and beetles are the only way to go. You will get far better results.
Trim off the majority of the meat. Scramble the brains and remove them. Fill a 5 gallon bucket up with water. Drop the skull in with a heater set at atleast 80 degrees. Make sure the water covers the skull. Let it set a week, than dump 2/3 of the water out and refill. Do this every week till the skull is clean. Should take 3 weeks.
Than degrease it. I start out wit a coupe weeks of dawn dish soap and water with a heater. After the dawn rinse the skull and let it dry for a week to see if you have all the grease. I usually finnish off with a week in acetone. Bears have to be degreased with acetone. Daw just wont cut all the grease.
One degreased let it dry a week and whiten the skull or seal as is. Once whitened rince let dry and seal.