Howdy, thought I'd share an easy to make tool to making it easier to sharpen.  The ideal is that you put the stone at the angle, and hold the knife horizontally as you move it.    This one I made is adjustable for many different angles. Move the dowel rods to adjust the angle. Use the angle locator to see what your is. Most swivel knives I've seen have an angle of 30 degrees. It's easy to move the different dowel rods in the different holes to get different elevations