There are serrated rubber wheels in a variety of sizes meant for belt grinders. That way you can get both flat and hollow grinds with a single appliance, just changing the backing surface.
I imagine that the greater flexibility of a serrated rubber wheel, compared to
- a wheel grinder, or
- a hard, flat platen on a belt grinder,
results in more rounding of the tool edges when a tool is pressed against the abrasive belt. I expect, though, that such rounding of an edge of the hollow grind is relatively easy to remove by hand honing on flat stones.
I imagine the following order of operation, for grinding a tool bit using both
- a belt grinder with a flat platen, and
- a wheel grinder or a belt on a serrated rubber wheel:
1. Using the flat platen on the belt grinder, with a course abrasive belt, do most of the metal removal: side, end, and top. (Aukai wrote above, "... I also use the belt quite often as a first operation with HSS.")
2. Using a wheel grinder or a belt on a serrated rubber wheel, perform the hollow grind on the side and end of the tool bit. Use a fine abrasive wheel or belt.
3. Using the flat platen on the belt grinder, with a fine abrasive belt, finish grinding the top of the tool.
4. Using flat stones, hone the hollow grinds on the side and end of the tool bit by hand. Don't hone the top of the tool by hand, because of the risk of ruining the edges with a facet. If you want to hone the top, use a honing fixture -- such as the one described by Conrad Hoffman in his article "Advanced Tool Sharpening" (link in post #1,828).
Caveat: In this thread, Mikey describes using a belt grinder with a hard, flat platen, and hand honing on flat stones, to achieve sharp tools. I expect that achieving it requires some combination of talent and practice. I am partly motivated to write this post by WobblyHands' statement in regard to honing: "Doesn't seem to be a skill that I have at the moment. Not for a lack of trying. But need to move on."(post #1,762)