The main thing is, try to match the wheel to how the hollow grind was made at the factory. That way you aren't altering the overall shape. A buffing wheel is much less precise, so it's not perfect.
You have 2 corners to worry about, the one between the edge bevel and the hollow bevel, and the one between the hollow bevel and the area near the spine. I sacrifice the corner close to the edge because it makes it easier to preserve the other one and it gives it a slight convex edge which actually makes it work better. But the curve of the wheel is close enough that neither corner suffers too much rounding for my taste. Here:
The edge doesn't blunt quite as much as you might expect, I assume from the direction the wheel moves and the resistance at point B. The wheel actually matches the bevel curve fairly close, but even if they were perfect the need to press the blade into the wheel a little makes it not perfect.
Don't push the blade too hard into the wheel, as that makes the corner-rounding worse. If it loses it's bite, use more compound rather than pushing harder.
I do most of this with the knife held left to right, and the edge hanging towards the floor. If there are some stubborn spots in the middle of the hollow bevel, I point the tip of the blade towards the floor and use the "corner" of the buffing wheel to put pressure on the middle area without touching the bevel corners on the blade. But that only helps with spots not close to the tang or spine.
I would like to use a smaller diameter wheel to buff out the final waves and imperfections that are often revealed (you can see some in the pictures), but the motor assembly is already close to the wheel diameter, so I would need a smaller motor device too.
