I prefer to remove as much flesh and tissue as possible and then boil the skull to remove all remaining flesh and tissue from a fresh skull, and a thin bladed fillet knife into the skull cavity to cut up the brain tissue so it will then just fall out of the opening in the back of the skull.
As for some of the not so fresh skulls I prefer to bury them and let mother nature and her bugs clean it, then wash and soak in a solution of water and a small amount of bleach, dont let the antlers come in contact with the water or the bleach will BLEACH OUT WHERE IT TOUCHED THE ANTLERS , AND NOT TO MUCH BLEACH OR IT WILL BEGIN TO EAT AT THE BONE AND I ONLY SOAK OVERNIGHT AT A TIME.
I dont use beetles at this time because I also do some hide tanning and Im afraid that if even one beetle was to escape it could make a meal out of the hides or capes.
Now this skull when I recieved it had been left out in the sun and the flesh that was left on it had dried like petrified Rawhide and it took alot of soaking and pulling to remove all the mummified skin, had to soak and pull, soak and pull etc over and over again. This is how it looked when I got it. Sometimes it takes alot of elbow grease