I sharpen my Head Knife ( Tandy ) with a diamond stone 600 grit. I don't know what make but the instructions were pretty good. Take the knife and drag it 10 times on each side, the 9 times, 8 times etc. When you get to 1 I've found my knife to be very sharp and all I need to do is strop it before and after each use.
I also purchased a set of KERYE stones. Four Hundred, 1000, 3000 and 8000. I use the same method and it's helped me get my Osborne skiving knife very sharp. The 400 is to get a basic edge on the blade but doesn't sharpen it. I push the blade in both directions and then go to the 1000 etc. These are wet water stones except the 8000. That stays dry.