I would use a flat 'honing' or 'sharpening stone' for at least the initial surface reduction, stepping to finer grits, utilizing sandpaper, on a hard backing, only as the final process, if required, to acquire the finish desired. The reasoning for this is that the stone will permit a faster and more even sum of stock removal this resulting in a more level surface and sharper, squarer edge definitions.

As this generally presenting more like a machine manufacturing execution rather than a hand one.

Scott.