I'm curious how that works out. I bought some silicone based fabric paint at the craft store that I was going to use on the under shorts of a running skirt I have that fits great but just rides up a little. I figured the paint was designed to be washed, so it should be OK, but I don't know if it'll be thick enough or tacky enough to actually work as a gripper.

I didn't even think of bathroom caulk or aquarium sealant but those are really good ideas, too!