You must use silicon carbide sandpaper (or diamond sheets or pads). The grains of aluminum oxide paper quickly round out and stop cutting.
I use the first two grits of sandpaper dry and the rest wet. I wash off the stone between grits and allow it to dry for inspection before continuing. I then use a crayon to note the place I missed and continue. You can use an old sheet of 1000-grit sandpaper for a few minutes between grits to bring out missed scratches. Tongue depressors, ice cream sticks, small flap wheels, cone-shaped tapers, and silicon carbide rubbing sticks all aid in getting into tight places. Silicon rubbing “blocks” are flat surface chunks which, when used wet by hand, can get the bumps out of a surface. (Bumps are often felt while not seen.)
Half your sanding time is on the first grit—getting out those deep scratches. Then the next grit might be 1/4 your time and so on. The last grit is a “breeze.” Scratches hold light. Get them out and the stone glistens.