What do you girls do on those damp humid days when your fondant/gumpaste pieces just won't dry/stiffen?

I make my fondant/gumpaste figure several days ahead to let them dry well. If I can, I place them on a cooling rack to let air circulate under them as well. You could try adding some gumtex to the fondant, that would help it harden more/faster. Adding gumtex to gumpaste, which already has gumtex in it, can lead to overly dry gumpaste that is hard to work with though, so use cautiously.

I have used the oven at the lowest temperature, switch OFF once it reaches the temp. and then place your pieces in, this worked for me when my orchids were falling off the wire.
You have to add tylose or gumtex to your fondant to dry hard.

Fan, lamp, and/or putting them on a bed of cornstrach.