Provide a humid hide and let the rest of the cage be.
Many people advocate spraying the heck out of the enclosure, covering screens with wet towels - yadda yadda yadda.
These steps are unnecessary and if coupled with lax cleanliness protocols, can results in the overgrowth of molds and bacteria - which can pose potential health risks for your snake.
Instead purchase some spaghnum moss or equivalent and soak it in plain tap water. Wring it out and place it inside the snake's hide. This will provide a humid microclimate that the animal can use as needed.
You can also place additional damp moss on top of the hide and around it.
Contrary to popular belief, ball pythons live in some fairly arid areas. They den in burrows and mounds that have higher humidity. By providing a humid hide and letting the rest of the enclosure be, you are not only making things easier on yourself, but providing something somewhat similar to what they encounter in the wild.
I use humid hides in all of my snake enclosures, from racks to cages, and across several different species. Even with the air conditioning running all summer long in the snake house, I find that I have to "recharge" the moss with water every three days or so. This beats the heck out of spraying things down once or twice a day.