It's not a polymer trainer: it's an actual knife with a sharp point.
I use the Spyderco Sharpmaker (medium, fine and ultra fine rods) on my Emmie...works ok, but not as well as it works on some of my other knives. I suppose I could try using them freehand, but I think I might just have mine professionally done. I don't really use it for utility tasks anyway.
http://www.defensedevices.com/kerambit-emerson-karambit.html
I use the Spyderco Sharpmaker (medium, fine and ultra fine rods) on my Emmie...works ok, but not as well as it works on some of my other knives. I suppose I could try using them freehand, but I think I might just have mine professionally done. I don't really use it for utility tasks anyway.

http://www.defensedevices.com/kerambit-emerson-karambit.html