I'm up in the air right now. I have a coticule and a Thuringian I'm still trying to figure out. I have succeeded at lapping film, but Jnat edges from the pros I've tried are sooo nice. Maybe I should sell my rocks, get Jnat edges on everything and call it a day. We'll see.
Film is easy but it has a "surgical" feel to it. No comparison to a great Jnat edge.