I taught with NOLS from 2001-2003.

When a NOLS course goes out, usually with about 15 hikers, 12 students and 3 instructors, they take one roll of TP with them for emergencies only.

The rest of the time, you make due with natural TP. My first choice if it is available: SNOW. Cleans as it invigorates. Very effective.

Second: western pine cones. They are thoroughly different from those I grew up with in the east. No sharp edges and they are basically brushes that work quite well. I've actually known students to fill a plastic bag with the softest, "downiest" pinecones they can find at each campsite so they have a ready supply of natural TP.

In Wyoming, Montana, Utah, Oregon, and Washington, I was always able to find decent wiping material. It just takes a bit of practice.

Back east, it's tougher. Rear-ripping pine cones and crumbling leaves Bad s*** in more ways than one...