I find boiling the skull works the best for me, When you boil add a small amout of dawn dish soap to help to cut the grease in the fat. Make sure that you dont allow the antlers to come in contact with the boiling water because it will cause discoloration and a change in tewxture to the antlers. I use a large rooasting pan and fill with water until skull is submerged, I place a dowel rod across the top of the pan and tie antlers to the dowel rod so they dont come in contact with the water.WhenI boil I use needle nose pliers to remove some of the tissues that are sticking to the bone and boil and repeat process. You can use a thin fillet knife etc to insert into brain cavity to break up the brain so it will come out the hole in small pieces.I think they come out looking better than when I bleach, bury, leave exposed to the elements etc.
If you use plaster of paris, remember if you ever drop it or bang or bump it the plaster will break easily. I found out this the hard way by using it as a filler around the bases of shed antlers that I attached to a skull.
The auto body filler actually works quite well and can be formed like clay in the beginning to reduce the amount of sanding.
If you check with some of the taxidermy suppliers on the internet such as WASCO you will find that they sell imitation buck skulls for mounting shed or removed antlers for european mounts, and they sell a device that you can screw shed or removed antlers onto for mounting plus they sell lots of plaques for skull cap mounts. Hope this helps you.