I greatly reduced the squeal on my car by putting high temp silicone (called ultra black) on the back of the pads - to stick them to the caliper. So that is something to try, just press the brakes once when it's wet and then let them dry in place. If you use the brakes when the silicone is wet it'll all ooze out and leave you with a lack of adhesive in the joint.

you can take the pads and coat them with anti squeal solution they should have it at any autoparts store also if the pads dont have a groove in the middle they are prone to glacing from the brake dust created when you brake. so servicing your pads may get rid of the squeal and it gives you a chance to find out where the noise is coming from.