I live in a very humid area. I don't use fondant to model anything - it simply does not hold its shape long enough to dry. Lots of people do use it, so you'll just have to experiment. I use straight gumpaste, or, very occasionally, 50/50 fondant/gumpaste instead of fondant. I was fortunate enough to take a Mike McCarey class, and I now looooove modeling chocolate/candy clay. It never "dries" - it just gets cold. The heat of your hand will soften it enough to allow changes if your shape or facial detail isn't quite right. When cooled, it remains as you left it. I just tossed a white chocolate clay high-heeled shoe I made two years ago and stored in a plastic shoe box (appropriate, yes? ) away from light and temperature extremes. Looked the same as the day I put it in the box. High temps in the summer months can obviously be a problem, but average room temperatures are fine for the candy clay. If I'm worried about temps, I'll use gumpaste. Gumpaste is probably the most permanent option, but even well-dried gumpaste will turn to mush within 4-5 days in my summer humidity.