you can mist the cage twice a day with a spray bottle, or you can invest in a "Humid Hide" (see the links below). A humid Hide is a cave type hide that is completely enclosed except for 1 small opening. You can place sphagnum moss moistened with water in the hide. The moisture will permeate throughout the cage raising the humidity a small amount, but the snake can actually crawl into the hide and enjoy the damp moss and curl up in it, thereby softening his skin and moisturizing himself if he's dry.
I used to use a Humid hide during times of shed, but I just leave it in the cage all the time now. My snake loves it. The sphagnum moss will hold humidity for about 2 days, and you simply wet it again. After several uses, throw it out and reload it with fresh moss.
http://www.bigappleherp.com/Zoo-Med-...c=2&category=7