I'm sure this is a trial-by-error type of thing, but has anyone hit upon any good tricks for filling the cookies with the crushed candies?
I have some small spaces to fill and I don't want the candy to end up on the cookie.
I actually did this two weeks ago with a group of elementary through high school age students. I did it with gingerbread dough, but I imagine it could be done with sugar cookie dough as well. We made gingerbread stained-glass ornaments, and they were absolutely adorable. What we did was roll portioned-out balls into long snakes and shaped them into the outlines of whatever shape we wanted on a parchment paper lined cookie sheet. All you have to do with the crushed candies is literally sprinkle them in, making sure you don't see space down to the parchment paper. Another method that I saw but haven't done yet is to use cookie cutters of different sizes. For instance, you could take a large star cutter first and then cut a smaller star with another cutter out of the middle, and then fill with the crushed candies. The candy (I read that Jolly Ranchers did the best so that's what I used) melted just like it was supposed to. When the cookie is done and the candy melted, take it out. The candy will become harder and harder as it cools.
I make rolled cut-out cookies using a sweet shortbread dough then use small cookie cutters to remove some of the dough inside the larger shape. I place this cookie dough on a sheet pan lined with parchment or foil. The cut-out area gets filled in with crushed hard candy. I've had success with lifesavers and generic hard candy. Bake at a low temp until the cookie edges are a very light golden brown; the candy melts and fills in the space. They are gorgeous!
Actually, there is another way. You can take some smashed jolly ranchers and melt them in a little bowl in the microwave. Watch carefully -- it doesn't take much to melt them! Then GENTLY pour into the areas you want and let set up -- all this after the cookie is baked. But please be careful, molten sugar BURNS!!
If you mean how do you get crushed candy into the small cracks and fissures in some cut-out cookies (suchas snowflakes), what I do is use a toothpick to "shovel" crushed candy off a spoon and into the open space in the cookie. Then I use the toothpick (one with a flat end, not the round/pointy kind) to encourage the candy crystals to go into the little spaces. The tiny end of the toothpick works well for this.
Sorry if I misunderstood your question, but that's what it sounded to me like you meant.