I've never owned that particular one, but I've owned at least one or two like it, along with several other carbide sharpeners. They take a bit of practice to get the most out of them, but you can get a pretty good edge quick.

A 16" flat mill bastard file does wonders with a Wensel Woodsman. The key is to use the same number of strokes on each side, with gradually decreasing pressure. The last strokes just barely touch. Keep the blades flat against the file--harder to do when the pressure gets light. Works great. Heard you can touch this up with leather and jeweler's rouge, but I haven't tried that yet.

Chad