What i find works is a small sharp knive. I kind of twist the knive down the base of the antler to the skull. Be careful not to dig to deep otherwise you will leave lilttle knife marks on the skull base.
If you do get some..i have used some fine sandpaper to lighten them up.
That stuff on there is thick membranes. The best way I remove it is by letting it cook off. And picking at it
It will take longer than an hour in the hot hot water. (Time, patience and a little elbow grease)
I also use a laddle to "baste" the top of the skull (if it has antlers)