Sandpaper is used to sand the bat faces, remove old ball marks and dings. So plenty around. I used it on the edges mostly...
The impact of a bit of roughage on one side of the ball is amazing. During net sessions we would score one side of the ball with an X using a bottle top. Mostly to teach youngsters how to handle a swinging ball. Anyone could swing the thing. I was in the team as a swing bowler and using that ball would usually aim off the pitch and let it come back. Great fun and a good training aid but never taken into a match though I only ever played regional firsts and district. Not good enough to trouble the selectors.