I use the little cups for guinea pigs that have the little wire hooks to hook over the wire sides of my coops for oyster shell. I also use that for the brooders, but depending on how many chickens you have, they may go empty quickly.
Just recently, I saw a post on how to make a feeder out of a plastic milk jug. Cut out two round holes on the sides for their heads to go through, and cut the top for easy filling, Voila! Cheap instant feeder! Better than the Qt jar feeders I was using, and less messy.