Paper towels are fine as a substrate, but when he is nearing a shed, it would help to raise the humidity & you don't want him sitting on damp paper towels-
so the best way to do that would be to add a "humid hide"- use a plastic food container big enough for the snake with quite a bit of damp sphagnum moss-
carefully cut a doorway into the container & he'll very likely be happy to use it...my snakes love sphagnum moss, & you can keep it in the cage all the time
also to help raise humidity.