Rock tumblers simulate the natural smoothing process that would occur in, say, a stream. It condenses the time from decades to weeks. So, really, it IS quick. LOL
Typically, you start tumbling with a rougher grit, water, and sometimes plastic pellets, and change it out with a smaller grit every week or two. Yes, the tumbler runs 24-hours, 7-days a week.
If you take the time and follow the process, it really does work. The rocks end up smooth and shiny.
PeggyS