Some of the guys on the knifemaking forums use a palm sander to cut down on hand sanding their blades. They generally mount the sander upside down in a vise and place the blade on top. It would probably work for the flats on your razors, but you'd have to make up some kind of curved bottom for the sander to make it fit the hollow grind of a razor.

I tried my palm sander on some of my knife blades but didn't have a lot of success. I put the sander on top of the blade instead of clamping the sander. That may have been part of the problem...