have you separated the centres without snapping any bolts? if you snap bolts youll need a machine shop to drill them out and insert M7 hellicoils. i paid 10 euros for every one snapped. i think mine had been overtightened in the past and possibly paint had also entered the holes! (so be sure to tape them over when redoing).
on the rim edge i used a drill with a plastic sanding disc to remove all the old clearcoat (paintstripper might have been an easier option but i wasn't sure it wouldn't stain the alloy). then coarse emery cloth on the outer edge for an hour or two per wheel keeping your hand following the direction of the circle always. the final finish is identical to the original but slightly duller but hey.
i didn't do anything with the centres as they are fine.
BBS USA confirmed torque bolts to 18 ft lbs (24 NM) and use blue loctite.