Thought I would share how I have done the polished stone technique:
Wet a cotton ball with rubbing alcohol, sparatically put two drops from a reinker(I used SU classic reinkers in at least two or three different colors) and a few drops of a metallic reinker on the cotton ball, then daubed it on a piece of cut-to-size glossy paper. It worked great at a workshop since you only had the one cotton ball to throw out and when it was dry enough to handle, it is already the size you need so you can continue with yor demo. Some of the metallic will rub off when handled if you don't spray it.
Kookie