Remove head from spine, skin out head, remove lower jaw, eyes and as much meat as you can. Other then that it's not going to hurt a thing if the skull gets a bit rank in fact some guys think they come cleaner a bit easier if they have some stink on them then there are the guys that let the meat rot off instead of simmering the head.
If you want to do your own skull it's kind of like cooking a ham hock, simmer the skull in a big pot with some Borax pulling the skull every 1/2 hour or so to remove what meat will come off then put it back in the pot. Once most of the meat is off the skull start again with new water and Dawn dish liquid to get the grease off the skull. A hunk of wire and a pair of forceps help to get the brain out of the skull. I also find a nylon vegetable / potato brush works good to get the stuff out of the tight spot. Once the skull is clean apply whitener and let if set a few days.
There's a bunch of video's and written info on doing your own European skull on the web from simmering, bugs, rotting and pressure washing.