I have installed tiles on the wall, they are not even natural stone tiles. I have made openings for electrical switches and outlets but now I need to make the area around these even so the cover plates fit flush to the tiles. So far I have tried using oscillating multi-tool with carbide grout removal tool to cut around and carbide rasp to remove the stone but the progress is so slow it would take forever. I am thinking of getting some type of diamond rasp but not sure if it would be any better? Also if someone can suggest another method or tool to do this job? I am attaching couple of pictures, first shows the tile and varying thickness and the second shows what I have done with the carbide rasp but I would have to remove much more to make it work. Any ideas?