Convex sharpening requires a different technique than regular "flat" or V sharpening. A convex edge is rounded, so the angle changes from shoulder to apex. The abrasives used should depend on the type of steel, the condition of the edge, and how polished you want the end result to be.
Here's Jason B showing how he does convex sharpening on a large blade:
[video]https://youtu.be/lx4odmy3zc4?t=11m[/video]
Brian.