My FAVORITE for D2 actually is wet/dry sandpaper (SiC and/or AlOx); SiC will eat D2 for breakfast. For convexing, avoid the mousepad, and use a somewhat firmer backing, like thin leather or a few firmly-backed layers of paper over hardwood or glass. For finishing edges on D2, convex or not, I like using trailing strokes on very hard-backed wet/dry sandpaper, over glass or hardwood. Diamond can be handy for setting bevels on D2 (or anything else), but it's not necessary for this steel.
For steels heavy in vanadium carbides (such as the 3V/S30V mentioned), I'd prefer to use diamond, at least for setting bevels; light touch-ups for finished edges could also be done with hard-backed SiC/AlOx, or diamond.
I emphasize firm/hard backing with the sandpaper, because it'll help the abrasive work more aggressively on high-wear steels. Used over glass, SiC wet/dry paper feels almost like a SiC stone. Sometimes it'll fall short on softer backing, when attempting to grind/shape the carbides in these steels, which is why I recommend avoiding mousepads and such. I generally would avoid mousepads with any steel anyway; they're too soft to produce really crisp edges in the finishing stages. The finer the edge becomes, the easier it is to start rounding off the apex if there's any 'give' or conformability to the backing.
David
