I use the green Scotch-Brite pads on my calls. I cut them into smaller, manageable pieces. You have to be careful using sandpaper on slate calls as you can actually wear the slate thin with sandpaper with too rough of a grit. Fine sandpaper works good for an initial dressing of the call occasionally, but the Scotch-Brite is what I take to the woods with me to touch up the call now and then.