First assess the antlers. are they from a fresh kill? are they still soft? Basically antlers are soft bone marrow with an outer lining of skin. The skin of which grows hair or what most of us call "Velvet" from the very second that animal dies, the blood begins to clot. Not any different from you or I. If the antler is still in it's growing stage or just about finished, the tips will be very soft and moveable. In this case you need to make a small puncture in every tip! do this with a large syringe or small knife tip. Hang the antlers upside down on on something and inject them at the base in the Main Veins, you will know where they are because the fluid will flow freely thru them. Also you can watch it go thru the vein. Continue this step on each point's base, and milk out all of the blood until you see only fluid. You can do this using the velvet tan or somesay with just a simple water/salt combo. Good luck up there and I hope it works out for you.
Joe