It has been a really long time since I've made Toba's Glace. I can't remember proportions as far as how much icing to keep out for edging and how much PS to add to the edging to thicken it up. Also, I'm trying to figure out how much glace I'll need for 200 3" cookies. I just saw this recipe on another site that indicated a single batch yields 2 cups but didn't tell me how many cookies it would ice. Any thoughts?
I keep adding PS until the icing is the consistency of peanut butter. As for how much you'll need, I'm not real sure except it's going to be a lot! I'd make one recipe and see how far it takes you. So much depends on how many colors you need and how good you are at guessing the amounts of each color to make.