I have used a coarse grinding wheel to get a slight “toe in” on the pad and the finish it with a second mill cut file . Once on my daughters Raleigh with center pull Wienmans the scratching brakes were too much for me . The pads looked ok but I thought a little too smooth. I took a flat bastard file and a couple of passes and viola . I have never gotten anything imbedded in the pad , but I would probably first try the grinder/file method and if that didn’t work , new pads and maybe smooth out the wheel to remove any grooves. If the grooves cut into the alloy too much then cracking is a possibility.