I never use straight fondant for making masks, bows or anything I want to dry hard and strong. I use gumpaste or even gumpaste with some fondant kneaded in, but I prefer the straight gumpaste for strnegth and fast drying time. I see so many people post that their fondat bow broke, they are heartbroken because they had put so much work into it and they feel their cake is ruined because they can't use the bow. I molded gumpaste masks over plastic face masks and had no problem getting them to release. I rolled the paste to a medium thickness, now as thin as for flower petals, dusted the ourside of the mask lightly with cornstarch, laid the paste on and cut around the eye holes and edges, let dry overnight. Next Day, carefully turn the whole thing over in your hand and the gumpaste shape should release easily into the palm of your hand. Then slip the gumpaste into the inside of the plastic mask so the paste can dry on both sides without losing it's shape. After it is completely dry on both sides you can paint it with Luster or petal dusts thinned with Evercler or some type of alcohol or vodka.
The only reason I think someone would use straight fondant would be if they planned to cut through the mask or bow and serve it to eat along with a slice of cake. But because of the softness you take that chance of it not drying completely and then cracking when you try and lift it onto your cake.