As you stated it is because you got nothing to do, tumble away! If graphite was messy it is because you put too much. A tiny bit is all you need and let the balls impregnated each other, no pun intended. I experimented tumbling and not tumble, ten each on a mesh over a coffee can half full of water. After 45 days or so, the tumbled with graphite looked as placed, the non tumble were white with oxidation. I have also experimented with Lee Alox, same results! If tumble right they should look like the attached picture!