I just made a glass call. I sanded mine with medium grit sandpaper, always in the same direction. Either blow off the dust or wipe it with a paper towel or clean rag, never with your hand. Don' t ever touch your calling surface or your striker tip with your fingers or hands. After sanding, work your striker against the sanding marks, not with them. The medium sandpaper should provide enough bite to work good, if not, sand it until it sounds good to you.