They said the rear passenger drum needed to be cut?

My car was makingan intermittent, horrific grinding sound, like something metal was dragging on the ground (so bad, I stopped to make sure nothing WAS dragging on the ground). That happened four times, when slowing down normally (ie. Not short). Took it to the dealer; they said the rear passenger drum needed to be cut, and they resurfaced the rear drums and sanded the brake shoes to remove grooves. I was able to drop it off a few days later; in the interim, I discovered a bolt in my rear tire, and which I THOUGHT might be the metal sound (ie. The tire was dragging, the bolt was being pulled along the ground). Brought it to the dealership, had the recommended drum/pad work done. After ~300 miles, the horrific, intermittent grinding sound was back (I didn't see a bolt anywhere in my tires, FYI). Didn't happen all the time; happens during normal braking (ie. Not stopping short), and generally only after the car has been driven at least 5 miles. Took it to a mechanic that was recommended to me; he said there was dirt caught in the brakes, cleaned the brakes and adjusted them. Not four miles after leaving, the grinding sound is back. And, now, there's a nice high-pitched rhythmic squeal that appears to be coming from a tire that gets faster as you accelerate. I'm getting very frustrated. Anyone? TIA.