If you want to properly preserve velvet antlers, you will have to inject & brush them with formaldehyde or some of the new less toxic chemicals (4 in 1 solution works great as does Knobloch's antler in velvet tan) as its  easier to use  however, both will work.

First, using rubber gloves take a razor blade and make small incisions at the tips of all points about 1/8". Next hang the antlers upside down, allowing the blood to drain. Starting at the bases inject the solution into the veins, you'll see and feel them that follow the antler. You will begin to see the solution force out blood towards the tips. Continue injecting the solution as you work the untreated blood towards the tips. When you reach the ends, make sure you've treated each and every  veins on each antler. You'll quit injecting solution when the color of the solution is the same coming out as it was going in.
Let the antlers hang upside down overnight.

After the solution and blood has stopped dripping out the ends, use a very fine painter's brush and lightly brush the velvet with the solution. This will prevent bugs from entering the velvet that has no blood. After leaving the velvet to dry, lightly "brush" out the velvet to give it the natural look. Remember to wear eye protection and gloves when using formaldehyde or any other chemicals. Slow down and don't be in a hurry to finish. When done correctly, your trophy will last forever.