CX500 GL500 650 Global

When I worked at a new car dealership, many of the journeymen made sure to put a non-directional final finish on freshly cut/turned rotors or drums. Most would use a medium-ish grit 3M gasket prep pad (roloc) on a pneumatic mini angle grinder. They swore that this was key to reducing squeal related come-backs.

The goal was to break up the tiny 'lines' left in the finish by the brake lathe. I think this worked in a similar way to royston's suggestion in that the non-directional finish would help reduce the amount of resonance and maybe even helped to seat the friction material.

I usually rough up my Drum linings with some 120 grit paper by hand and never seem to have any Shoe squeal and of course take the glaze off the shoes and chamfer the leading edges of the shoes