check your belt before you by a new one, take it off flip it groves out, and bend it, if there are cracks and chunks missing, get a new one, if its real dirty and no cracks clean it with warm water, dish detergent and a scrub brush, dry it and re install it.

while the belts are off, take them both off and check them, turn all of your pulleys make sure they spin free and have no excessive play in them.

and belt dressing is crap, dont bother it last like an hour and the squeal is back.