Conclusion so far.
If it is sticky, it is mucus, if not, it is sweat. Reason for mucus is something is touching the mucus gland in the anus, could be piles (enlarged hemorrhoids) or stool. If there is feces with the wetness, it could be stool, but feces can also get trapped by hemorrhoids, in which case you're probably often not clean after wiping the first time (you tried).
The wetness does not cause smell, neither sweat or mucus should have this smell. We need to:
- Figure out if it is enlarged hemorrhoids and remove them if possible
- Somehow strengthen the anal canal to prevent leakage
We need to watch out though, pressure/clenching etc can cause hemorrhoids, so not sure how to go about point 2.