I use a multi-speed dremel on low setting with the 5/32, 3/16, 7/32 stones and I have very good luck with it. When chains get wore down I switch to a worn stone of the next size up and file the rakers down a bit and I like what I get. The grinding stones don't hold up well but they are cheap. I use a 1" square of 4" long wood with 30 degree lines drawn on it in the shape of a "w" to hold against the bar as I grind to give me a constant angle to shoot for and hope I keep it at 90 degrees perpendicular to the bar. I count 1001, 1002, and move on, using a light touch. Sometimes I do better than others but mostly I get chips coming out the back of the saw.