The punch line is that just about anything will work, but some things work much better than others. Besides the leaves, one of the best toilet paper substitutes can be found in the winter or at high elevations, and that is snow. Wet, packable snow balls or snow chunks work best. Yes, it's terribly brisk. But it's the cleanest thing out there, and it works well. The next best things down from snow balls are bundles of dead grass, bundles of fibrous inner bark, or rounded stones or shells.