One of the few things my Dad taught me rather than my Great Gramps was putting an edge on a knife. Gramps was good. Paps was better. I guess they both taught me. But I just don't seem to be able to hold the knife properly anymore for free handing. I can still do a passable job to most, but passable just aint in my vocabulary when it comes to my firearms or my knives. Wife drives me bonkers. What she calls sharp is what I call dull as a damn hammer. She can't seem to figure out that if she doesn't let me know one of her kitchen knives is dull, it just makes twice the work for me to bring it back to a good edge to where the knife is doing the work, not YOU. That is how people get fingers cut off.
CI, with all the fishing you do, I would imagine you go through way more than your fair share of filet knife edges. After I do one of mine I'll let you know how well it works on a thin bladed filet knife. Going to tackle those tomorrow. You would probably be best served with a diamond set like mine since I'm sure you probably go through them like hot cakes.