sqeaking belt

Recently I have noticed my power steering belt was squealing, and was pretty loud if I reved the engine. So we put a smaller belt on it. If I push down on the belt it goes down about 1/2inch which is what it should be. The alternator belt is the same. It helped a little but still sqeaking. So I squirted all the pulleys with belt dressing, even cleaned it real good when the belt was off. Still doing it. Any suggestions. Thanks