I use the sandpaper for my jewellery tools, so since they dont need edge cleaning i rarely start with something coarser than 800, unless a graver falls tip down then a 400 does quick work of a nick, think rusted blade or rebuilding the edge 400 and coarser, oxidation spots 400 and finer, just resharpening finer than 800.
Gravers can use down to a 2500 and a finishing pass onto a rubber pad to clean the edge, but those have to leave a mirror finish when they cut in metal, woodworking i dont even bother to go to 2000