I use wax paper to close off one or two top halfs of the walls, both being the corners that meet. You won't have to worry about mold forming on it and the water rolls off it with ease. I'd be concerned leaving a damp towel there since your chancing mold or bacteria to grow or I feel it'd be a pain to change it everyday. If he's got stuck shed you can try a shower. If he's an adult the shedding process could take a few days as they typically shed different parts of their body at a time. If he's young and it's taking more than two days, like I said, try giving him a shower. There's threads on here that explain how to do so if you aren't sure how.