I know from speaking with Valery from the Gentleman's Den, that he will not use power tools of any kind on his razors. He does everything by hand, and as mentioned above, up to 10 hours of sanding wouldn't be unusual.
When I was sanding up the I.Barber Anchor razor (still more work to do), I gained a vague idea how much work, concentration, and care goes into restoring these blades to such pristine condition.