First of all I am aware that a lot of you do your sanding dry and do a great job so I can't knock it. As a proclaimed amateur having fun (most of the time, anyhow) find that wet sanding works best for me for several reasons:
1.The sand paper lasts longer without clogging - my estimate is 3 to 4X as long and the Scottish side of me is happy (did I say that I'm leaving for Scotland next week for 2 weeks for reindoctrination and few wee drams of uisce beatha)
2. The wet surface keeps the sanded-off substrate from building up under the paper so you don't end up sanding with the dust
3. The constant flow of fresh water keeps the rest of the surface reasonably clean and shop dust down to a minimum.
While I can't always use a dribbling hose on the many separate pieces such as from this '31A, I am using it on the body proper. A modern integral fendered car, using a hose is easy.
There are a couple of downfalls to this:
1.Your hands get nice and soft and wrinkled (your significant other might appreciate this though
) then cut easily if not careful.
2.You are usually standing in a puddle of water, and depending on the time of year, might be uncomfortable, especially if you are using a dribbling hose
3.Any buckets of water need to be changed out regularly and dumping it into the yard or driveway is messy. A small shot of Dawn dish soap in the fresh water makes the water "stick" better and provides a sheeting/clearing action on the panel.
One caution - if you do drop the wet sandpaper on the ground, throw it away or as a minimum rinse it off anywhere but in the bucket. I picked up one grain of dirt and made 2 long scratches in my fresh poly primer before the brain kicked in and said stop(did I say that wet sanding tends to be brainless
). They weren't that deep but could have been.
Now - back to softening my hands again