How to use a rock tumbler - a quick and easy guide. Have you ever walked along a beach or a riverbank, and found a rock you just had to have because it was so smooth and pretty? Over many years water, wind, smaller rocks, and sand have ground against that stone (and others) to achieve that look and feel. It could have taken a hundred years to get the rock to that point! Luckily for us, you can do it yourself at home in just a few weeks using a rock tumbler, and a little bit of patience.