I've heard people mention this and wondered....

A. What is the procedure for wet sanding?

and

B. What does this accomplish over just regular sanding?

As always Thanx in advance for the help

I use wet 600 paper for fine / finishing work after primer , call it lubrication !
I sand by the sink using a big sponge I wrap the paper loosely around it like a sanding block to give a soft base and end up with super smooth surface...and can wash off the paper as i go to keep it relatively clean.
still using the same peice for a while ! :btu:

I wet sand bowls sometimes... I soak a piece of wet and dry paper in water and sand with it dripping wet 220, 400, 600. You don't generate the heat and it raises the grain some. You need to let it dry before you finish, hard woods like curly maple smooth up nicely.

I don't see a need to wet sand plugs, the primer fills in most of the tiny scratches.

When wet sanding you want to use a sandpaper that is rated for wet sanding - one that won't tear easily when wet. This usually means using Silicon Carbide (black) paper or maybe an Aluminum Oxide. Garnet paper will not work. Any sandpaper that you find in an auto parts store should work since body work is generally done wet. There are also snding sponges and cloth backed materials. Wet sanding is best when you are doing the finer grades.