I am having trouble keeping humidity where it should be in my BP's tank. My humidity gauge broke so I am working on getting a new one in the upcoming days, but I could tell my tank is dry and my BP had a bad shed. I WAS using newspaper but switched to paper towels, hoping it might hold more moisture. I have limited ventilation, since I have a screen top, but it doesn't seem to work. I try to mist regularly. Are there any other ways of keeping proper humidity?
Would using a substrate work better? If it does, I'd probably go the route of using aspen. I have questions on how often I should change the substrate.

Thanks