I need to remove about .5mm of material from the "south" side of a humbucker pickup rout. This is on an archtop. It's a small amount and a curved top, so I don't want to use a router. I have heard of people doing this with a rotary tool. I have one, but am not very skilled in its use. What is the best way of doing this. Should I use one of the sanding cylinders...or is there a better way?