use a thick film of soap on the knifes surface to prevent scratching.. this one works, its a way better option of having a machine do it or a pro that will just grind a new edge on every time and eventually you end up with a boning knife, forget that, I just picked up a $180.oo trident, no way is a machine going to touch it.. use the guide, after a while you feel the right angle, practice like anything, I start off with my more inexpensive knives to get a good feel it works its stone, you need to be able to determine if your knifes edge is still there or destroyed, if its gone you need to re edge it, a heavier stone.. then there are two distinct style of sharpening any kn9ofe, single edge or double edge, double edge keep the knife true through the material, heading straight, single edge they tend to veer off.. keep the stone wet and use a tiny lil bit of soap