Using a substrate that holds humidity well (like Eco Earth) is always a good first step. Moss also holds in moisture and you can even wrap some around branches. Live plants help too but I think you already have some?
Another option is at least partially covering the screen top with saran wrap or something similar. I did that when I had a dart frog terrarium (they require even higher and more consistent humidity than cresteds!).
Your tank shouldn't grow mold from the misting as long as you're cleaning it regularly. By the way, how often are you misting the tank and how much?
"We weep for a bird's cry, but not for a fish's blood. Blessed are those with a voice."