just did 2 this week, and up until now its just a matter of patience, i did try something new this week and it worked 'pretty good' i mounted a router on my tool rest and slowly turned the antler by hand and edged the router in with every rotation, needs a lot of fine tuning but i rounded 5 blanks in the time it took be to turn 1 the normal way.
disclaimer:i am a trained professional, don't try this at home,