I'd probably use paper towels in your situation and just create a damp hide if you're having humidity issues. They are super absorbent so when soiled it spreads more, creating a larger target for you to locate via touch. I would also have an extra tub per snake, ready to go. They can smear feces in the strangest places and if I couldn't see clearly I'd just feel better making sure I completely cleaned and disinfected the enclosure after each bowel movement. Water bowls are a favorite place for some snakes to relieve themselves. I change mine weekly but check twice a day for any soiled ones that need immediate cleansing. If I were doing this without sight I'd probably just change waters daily, making sure to dump them in the toilet first just in case.

The easiest thing to do for a damp hide is just run some water over sphagnum moss, squeeze out excess water, then fluff it up a bit and toss it in your hide(s). Make sure you get plain, 100% sphagnum without fertilizers or pesticides added. You could probably just change the sphagnum every month or when you smell something fowl in the hide. Paired with paper towels I'd switch to a fully enclosed hide(like a dark tupperware with a hole cut out in the top or side) as opposed to bottomless, cave hides most folks use. This will keep the moisture from soaking into the surrounding substrate and possibly tricking you when you're feeling for soiled spots.