Any edge can be convex. On a hollow-grind blade, because the metal behind the edge is already very thin (this is the main attribute of hollow grind, which improves slicing in thicker materials), you wouldn't likely notice as much change in cutting performance as with a thicker blade (which benefits most from convexing). This is because not a lot of metal would be removed by convexing a thin edge anyway. The rounding and smoothing of the bevel shoulders will always reduce resistance to cutting, but the improvement would be less noticeable, assuming the edge angle isn't significantly changed in the process (from obtuse or very wide, to a more acute or thinner angle).
The easiest (and usually best) way to convex an edge, especially a thinner one, is by using an edge-trailing ('stropping') stroke on sandpaper over a slightly forgiving backing (like a hard-backed leather strop). Stropping technique on somewhat soft backing (leather) will always tend to convex anyway, and using the same technique on sandpaper will simply do it faster, and remove metal more aggressively. Any freehand method, including use of the Sharpmaker, will result in at least some convex, simply because the human hand won't perfectly maintain a consistent angle on each and every stroke. More often than not, trying to deliberately convex on the Sharpmaker will more likely round over the apex of the edge, in addition to the bevel shoulders, which will just dull the edge. Great care must be exercised, to avoid rounding the apex itself. The Sharpmaker's setup is geared towards minimizing the 'user error' in angle control (just maintain the spine of the blade at vertical), so deliberately attempting to convex would sort of defeat the main advantage of using it. It's better-suited for V-bevels, in keeping them as flat and crisp as possible, without actually using a guide to hold the angle.
One of the reasons I personally like convex, even on hollow-grind or other very thin blades, is because it can be maintained using exactly the same techique & stroke (edge-trailing), at every single step of grinding, honing or stropping. Only thing that varies is the grit at which it's done. That helps in a big way to refine technique and maintain consistency throughout the process. So, with some practice, sharpening gets very, very easy, from beginning to end.