No different than any other head you have done with a few exceptions, size and horns. Size, everything is bigger, need bigger pot more water etc. Then horns are all you have to deal with. Mike in his tutorial rotted the sheaths off. You can also simmer them off or sweat them off. Get them off, cut the cores down to help with the size and deal with the head as you normaly would. Here is how I got them off a old steer:
http://www.taxidermy.net/forum/index.php/topic,264750.0.html