The point is that there should be water between the paper and the rubbing surface.
The surface is supposed to become dull, of course, in addition, in the places of scratches, it must be ground evenly to the depth of the scratches - so that they disappear.
The surface is supposed to become dull, of course, in addition, in the places of scratches, it must be ground evenly to the depth of the scratches - so that they disappear.