Trying to tidy up a slate surface that has many shallow scractches (deepest
probably only 0.2mm, most less than this). Have tried sandpaper, glasspaper,
metal sanding disk, rust removing disk, slow speed, high speed, with and
without water - all to virtually no avail.

People say thaat slate, being a very soft stone, should sand no problem -
where am I going wromg ???

Thanks