The best wet sanding results will come from not using your fiongers..Always use a soft block..I use foam roll bar padding for concave curved contours and a std rubber sanding block for flat panels. Larger convex curves I use a peice of havey rubbr, slit so it conforms easy to the body as you move it. Lots of water..a few drops of dishwashing soap in it will help a lot. Replace the paper often, and go like they said, until all you see is flat grey. Dont worry about the color coming thru just yet..This method is labor intensive, you'll be sanding a rolling a lot from what I have read. I usually wet sand primer, then spray all the coats of color..then wet sand again, do any graphics, then spray clear, wet sand that, and buff. So even doing it "the old fashioned way " takes a bit of effort. Probably what drives all the body men to be criminals..

Almost forgot..If you drop you paper, block, or sponge (to dribble the water over the surface...), dont rinse it off in the bucket with your sanding water..Sounds stupid, but you'll end up sanding with gravel from the pavement if you dont be careful...