theory11 — Magic Tricks & the World's Finest Playing Cards

How to soften coins?

It's really not worth softening the normal Aussie coins, unless you're using the old round 50c coins which are made of silver. In which case, you could use sandpaper or a file (not recommended as it doesn't look that great). I would suggest using a tumble grinder (basically a jar or container with ceramic bits or ball bearings in it that shakes or tumbles) which would give the coin a nice even softening.
 
I know I am asking a lot of questions, but what are they made of, because thats what matters.
 
I believe you go to the hardware store and buy the wet sandpaper, and wet it and use that on the coins to smooth them out.