Agree! If you only need a slight humidity raise (such as when my corns are going through a shed cycle) a damp towel usually does the trick for a couple of days, but for long term use plastic wrap or plexiglass to cover 50-70% of the screen to prevent humidity from escaping. You can damped the substrate, but also make sure you don't keep *too* wet or else you risk your snake developing scale rot on their stomach.
Good luck!