Paring knives a pretty cheap and due to the blade sharp easy to work on. I've had some issues with using a Victorinox paring knife to learn how to sharpen on due to it being bent and blade concaved in the middle of the blade. I actually thinned it out so it bug me less.
I don't know paring knives all that well but from taking a quick glance at what to replace my practice sharpening knife with I was looking at Opinel and Old Hickory, they each set you back $10. Though any old kitchen knife or knife will do the trick, preferably a cheap one you don't care about. I just prefer taking things one step further.
Beyond that I would ask this question in the maintenance, tinkering & embellishment section they would help you with convex edges.
Though off hand if you ever reprofile a blade and want to convex it and you have a lot of metal removal I imagine it might save you some sandpaper if you do the major metal removal by stone before moving to sandpaper to convex it. (Disclaimer, I don't convex blades this is just what I suspect will help)
