if you are going to machine down the brake disc make sure the machinist has proper tools for it, it should be tooled from both sides in one go - it ensures the disc remains true, also make double sure you are not going too thin on the discs otherwise they will warp under brake load - check the thickness - it should be stamped on the disc itself.
If you are just removing glaze, use coarse emery cloth to remove the shine and install new pads, I had a more easy way, I made a set of disc pads with soft grinding stones on them, I drove the car around very carefully for about half a km and applied brakes softly and constantly, it removed glaze from the discs..
It is a very high risk procedure because you only have about 20% brake power compared to normal working brakes.