I had a caribou preserved by freeze drying. I cut the antlers off the skull, and the taxi freeze dried them and I put them back on. I think it cost me like $90, and took about 30 days to get them back. I think it would be really hard to keep the velvet intact on the skull and not mess it up no matter how you clean it up.
When I killed him I pricked the ends of the antlers and pushed the blood out and also pushed them out the base best I could. Kept it cool and dry like meat. The antlers were very hard underneath though. Spongy antler could be a problem though. I would think your best bet will be freeze drying. There is probably blood locked inside the antler that will just rot over time and I doubt you can preserve it with other methods. I really don't think putting it in a freezer for later will save you much time. Blood is much different than tissue. It might by you a little time, but being ready to preserve and have a plan for immediately after its killed, I think is key. I've heard of submerging in alcohol, acetone or borax, as well as the velvet preserve or velvet "tan" solutions and pickling. Freeze drying seems to preserve the best shape/color though.
I usually just strip it off now and don't worry about it. I think the window of preservation success is also very dependent upon the velvet timing and how close the animal is ready to rub.
The velvet on this bull was really tight and stayed on. I've shot some that you could peel it right off and was lose on the antler and others that were very tight, but were weeks out from stripping and the last 2-3 inches of the tips were really spongy.
There is also the spray on option. Its gotten a lot more realistic in the last 5-10 years.
