I have been painting skulls, bone, rock whatever I can get my hands on for years.

The cattle skulls I use are from our own cattle. We raised Corrientes and Longhorns for the purpose of roping and we always fed out the older steers for our own meat. There are many ways to prepare, which I have learned by trial and error, Mostly error! when I get the heads they still have meat on them but are skinned, if you have a pond?  tie a metal fish stringer to it and throw it in and leave it about 6 mo. you can also bury it or you can just hang them on a fence post and let nature take its course. But, if you leave it outside, as it dries the horn caps will loosen and the squirrels will steal them so be sure to tie them on with wire? These heads pictured are old dry and ready to clean.* They are without horn caps

1st. I spray them down with OXY CLEAN then let it set for a bit

you can also use other cleaners, bleach blends are Ok, I like the Oxy

2nd. I prefer to power wash, if you dont have one go to the car wash and plan on getting wet and dirty!  I loosen and knock off any sharp edges with a hammer" WEAR EYE PROTECTION!  sometimes you have to score it with a hand saw first. but just try to get the back smooth so it will lay good. From this point I dry in good sun for several days, once again secure or put where nothing can reach or they may disappear. Next I spray paint or clear seal, dry again then paint my picture and reseal again. If I am going to put horn caps back on I will sand, polish and seal the horn. Then put a little glue inside when you slip them back on the horn base. I will be painting these steers and a deer skull for Christmas, Check back soon!