The sheaths will seperate from the skull,if you let it sit out. You can speed things up by placing the skull in a plastic bag. Use some borax or any like detergant and boil the skull part and allow the sheaths to air dry. The boiling cooks out all the tissue in the bone. Allow to air dry. If you're going to do a european mount,take care of the skull bleaching now. I spray lysol in the sheaths,but to be honest,the sheaths have never had odor. I then take BONDO and place a generous amount in the sheath and place it back on the skull. While the bondo is still hot and pliable cut the excess off around the bases.

Whats Bondo? I've heard of this before on a Taxidermy Video. Is it like a putty?

Bondo is a brand name of an auto body filler. The two part putty that gets rock hard and is sandable and paintable. It works well as a filler for the horns because it flows well before setting.
It is not an adhesive so you can get in trouble with attaching horns. They have been known to pull off when using bondo.

Thanks mate. I'm going to try my hand at a pig shoulder mount this dry season, this talk of bondo had me thinking of where to get this stuff