Brake Reface

I just had my front discs and my rear drums refaced....after a few days theres this "rolling" sound that comes from what i think and i hear is from the rear..do drums need to be "scratched" with sand paper? coz i didn't see the mechanic do it....usually when you had your brakes cleaned they do this.

btw the sound is like "eeeeeeeewwwwwww" the sound is not audible the moment i step on the brakes. i just hear it when im slowing down...

need your inputs guys.