Depending on how long you are on the trail, toilet paper can run out, then what? I usually don't bring any to begin with and wash with soap and water instead. It's MUCH cleaner than using/hauling around toilet paper. First wipe with local vegetation, 'lambs ear' works well, leaves, soft grass...then wash/dry. The stuff you are wiping with is likely cleaner and more fungus free than you are.
Same goes with cleaning pots. I don't use sand/gravel. I will use bark/leaves/grass, then soap/water. The detergent/soap part will usually be Dawn or Dr. Bronners, along with a chunk of "camp towel" as a utility rag.
Remember, most of the world doesn't use toilet paper. Then ask yourself...are you cleaner coming out of the shower or off the pot after wiping? I'll bet you're rear end is cleaner coming out of the shower.
No fungus's or other problems in over 30 years of hiking/camping.