I used an alum block on my face for a long time.
It didn't do anything except dry my skin horribly.
In fact, my skin was just hurting until I picked up some Thayer's, but that's another story.
Anyway, I'm reading on here that some people use the Alum block to make their fingers tacky to stretch the skin.
So I give it a try.
Did that ever work well. No slipping or sliding around.
If you have one and you're not using it, give it a try on your fingers.