"Keith Young" writes:
What are the proper techniques for water sanding. EG. Type of
sandpaper and how to use it etc?

There are three techniques, wet sanding, grain raising, and grain
filling.

Wet sanding is for sanding hard surfaces that result in a fine powder
(i.e. film finishes, metals); the water helps clean the sandpaper and
wash away the powder so that the sanding can proceed without clogging
up. For this technique, you'd want the item wet while sanding, either
by rinsing it, running water over it, or rinsing the paper
occasionally. You need a waterproof sandpaper for this, I usually use
sillcon carbide wet/dry sandpaper.

Grain raising is different. If you have unfinished wood, what you do
is rinse the wood and let it dry, then sand off the raised grain.
Repeat with finer and finer grits as usual. The result is that you
have a piece that, if it happens to get wet (washing or water-based
finishes), won't get that fuzzy feel. In this case, any sandpaper
will do, and you'd use compressed air or a tack cloth to remove the
powder.

The third case is grain filling, or wet sanding with a finish. This
is for grain filling, such as a french polish. What you do here is
use a wet/dry paper with an oil (instead of water), so that as you
sand the powder gets trapped in the grain with the oil, and dries that
way, filling the grain.