For mine, I use a combination of paper towels and about 4" of litter. I stir it up on a regular basis. I've had the chicks one week. I plan to dump all the litter tomorrow and put in fresh. I like using the paper towels in the primary area because it is so easy to clean. I put 3 half sheets in the main area and 1 half sheet under their food. I have their water dish sitting on a brick, paper towel over the brick (learned that the hard way). I change out their water twice a day (before I leave for work and then after I get home).
So far, this seems to be working for me. I will probably have to start changing out the whole brooder several times a week as the chicks are growing up fast.