There are several things you can do to minimize brake squeel, but it could return.
Remove the pads, sand the lining to remove any glaze. Use a very course sand paper. Lightly champher all edges of the pad with the sand paper. Scuff up the rotors with the same sand paper, or have the rotors machined. Remove the rotors from the hubs. Clean any rust from the surfaces where the hub and rotor mate. Gently apply anti-sieze compound to those surfaces. Make sure the caliper slide pins are working smoothly and are properly lubricated. Where the back of the pad backing plate mates with the caliper, either treat with anti squeel goop (preferred) or lubricate with disc brake grease. Also lubricate the pad backing plate at any point that it touches the calipers. Reassemble.
The most critical part of all this is the proper lubrication of the brake pad backing plates. Unfortunately, often the most neglected part of a good brake job.
