As long as you re-hydrate it it should loosen up enough to cut it off. A final peroxide soak is always a good this when preparing a skull. I typically use washing soda/soda ash in my water when I "boil" a skull. It breaks down tissue faster than hot water alone. Then the peroxide finishing with a mat clear coat. Just watch getting the peroxide on the horn, it may lighten it. I know it lightens antler, but you can put the color back with wood stain.
