Max,
Put the head in the clamp with the base of the ferrule tight against the jaws then swing the tip out to get the blade you're sharpening as close to parallel with the front of the clamp as possible. Then color the bevel with a magic marker. Eyeball the angle as close as you can, then take a couple strokes with a dry stone and see where the ink was removed. If the ink is gone from the shoulder of the bevel but not the cutting edge, that's telling you the angle is set too low. If it's taking the ink off the cutting edge but not the majority of the bevel, that means you're angle is set too high. Adjust till the dry stone removes the ink from the whole bevel then sharpen the head just the same as you would a knife. It's important that you finish with into the edge strokes, flipping the clamp every pass. I use all three grits unless the head is still very sharp to begin with. Give that a shot and if you need more help give me a call.
Ron
800 561-4339