Pastillage dries very hard. But the down side to using it, is that it also dries very quickly. Because of that, I do not use it for figurine faces.
Your other edible options are rolled fondant (sugar paste), or gum paste (flower paste) , or modeling chocolate.
If you can use non edible then go with polymer clay. It stays pliable until you bake it.
Choose your sculpting medium based on your skill level. Fondant and gum paste harden much quicker then modeling...