Excellent for flattening Japanese waterstones, drywall screen is a mesh based abrasive designed for sanding very soft friable materials. The powder that is removed goes through the holes in the mesh, so it doesnÌt clog up.
Stretch the drywall screen over a flat surface and hold in place with a couple of bulldog clips. Used dry it is very fast indeed, if you scribble over the face of the stone with a pencil first you can see your progress.
Also very good for its original intended purpose of sanding plaster and surprisingly good for woodturning.