I do all of my own. DONT USE BLEACH!!! It’s destroys the bone!
I also do not boil or simmer, I macerate them with a bucket heater. Once all the meat has “melted” off, I rinse them really well and then (the most important part) degreasing. The skulls have to be fully degreased or they will yellow and “bleed” grease over time. Once they are fully degreased, I get 30 or 40V peroxide from a beauty supply store and paint it all over the skull and then set them under a heat lamp. Repeat until you get the desired results, but be aware that every coating of peroxide destroys a little more bone. Be extra careful with skulls from young animals as they are much more fragile and will come apart easy.