Jeff, I don't ahve a Yard Hook but I have had a few re curves and still own a kukuri.
I would suggest gettin some different grit sand papers. If it needs serious work look at starting with 100 or something, maybe 220 and work up from there.
If you use a narrow edge (like 1/2" or 1") surface you can sharpen as you would on a stone with a straight edge.
Remember to keep the edge perpendicular with the paper. As the edge curves it needs to be held square to the sharpening surface.
I hope this helps.