I basically use the same technique Mark uses on the course of different grits of sandpaper using a fret file. I use one of these. https://www.thomann.de/gb/gewa_bundfeile_150mm_hieb_3.htm?glp=1&gclid=Cj0KCQjwnqH7BRDdARIsACTSAduDw3Ri22bTKXcagDU4aWA36NfN_Gt27fmXKWHGjrj0k8SLQJDCQFMaAlokEALw_wcB I then us A fret end file and finish with wire  wool. I have been…   Read more»