I had humidity problems when I first switched her from tub to rack, our apartment is *very* dry (between 20 and 30%). I switched over to coconut fiber for both cost, and how great it is maintaining humidity. I can get a brick of it at the home and garden store for $1.99 which will last me a month once it's absorbed the water properly and enough left over for spot cleaning through the month. Plus, the extra has also worked great for the house plants as well! I find using the coconut I only need to mist once every day to 2 days, and getting humidity bumped up during shed is a breeze (I typically just do a full switch over with fairly damp fiber whenever she's going into shed - then perfect every time).

Instead of baking it before hand I "disinfect" by using boiling water on the brick - it serves to kill any bacteria and also convert it to dirt form quickly.