you can sand it wet or dry, both have their positives and negatives. dry there's dust, wet there's sludge. Personally I think wet is faster but some will argue the other way. Try it both ways. make sure to use a guidcoat and use the longest block/board for the job at hand.
What i do at work on a old car and some other cars i work on, i prime and then block 180 dry, reprime and block 180 dry, prime and dry sand 400 then seal and paint..... ect. Like badbob said use a long block when ever possible so you dont put a wave in the body. If working on a long bodied cars i have seen a dura block that is about 30" or so long. these are nice because it will eliminate the possibility of "the wave" Mike
i wet sand everything. i do not need the dust in my lungs or in the shop. as for sludge i have none. i keep the car rinsed. when i'm done it is nice and clean. i have a 1/4 in hose with a bug sprayer nozzle on it.
I've done it both ways, I prefer to wet sand (when it's warm)
because I can see what I'm doing better, when dry sanding the dust
seems to get in the scratches and hide my guide coat.
The wet just seems to do better, but that's just me.
I also have a 1/4" hose, like Shine (He's bragging,LOL).
I got an adaptor from Home Depot to connect it to my garden hose.
I also glued a clamp on a speaker magnet (w/tape on the bottom)
to hold it where I needed it. Works really good. imp:
3M makes clamp on 18" wet or dry board paper in grits as coarse as 220, and I've seen other manufacturer's sell it from 80 to 400. Sheets 9X11 are available from 80-2500 in wet or dry. Do an abrasives search.