i used large flake pine shavings, but when they were itty bitty i put paper towels on top for a few days & then switched to puppy pads. i used them for about two weeks. i was real happy with that.
I remember someone mentioning that they use chick starter (crumbles) for bedding. It makes sense since most of their starter gets lost under the bedding, anyway. When I clean out the brooder, after the chicks are moved outside, I am amazed at the amount of chick food that is in among the bedding that I'm throwing out!