i use moss, the rehydrated bricks of it
i boil water to expand it and kill off anything unwanted (mites mainly)
after it cools i wring it out real good and lay it around the water dish
every now and then (couple days) rinse wring and repeat
you can use more or less and adjust to get humidity where you want it
some people put it in a conatiner with a hole in it for the snake to crawl into
but around the water bowl is good for me i got one female whos prone to scale rot so i dont like her laying on anything moist for very long
hope this helps
oh you can mist it if your in a hurry to it soaks up water like a sponge