Use humid hides. They can be as simple as placing damp moss inside the hides. This will make the humidity in the hide higher than the rest of the tub. Using humid hides you may still need to mist but nothing like you would without them.
Cypress mulch is really good at holding moisture too. I have three tubs that don't hold humidity well and switching to cypress mulch alone has helped my sheds a ton. I still mist daily. The only reason I done have humid hides in them is the bloods are out growing their current hides and simply have no room for it. When they get a bigger tub they will get the bigger hide with moss. I also use moss when a hide is to large to make it seem smaller to the snake and adding a more secure feeling.