Yeah, I wet sanded between coats with 400. Its nice, no dust, and the sandpaper lasts for ever. I just keep a little spray bottle to keep the panel wet. The sanding in this case is to provide "tooth" for the next coat to adhere to. I'm a wooden boat builder, so it's just like varnishing to me. I roll it in small sections with a high quality super short nap varnish roller, and then tip the paint with a high quality brush. I like the Purdy hand made brushes. If it's warm, and you mix in just the right amount of penetrol, the paint lays right down and there are no brush marks. I had a few runs of course, and a few brush marks. I waited several weeks for them to cure fully, and then scraped them flat with a razor blade. Then wait a few more days to make sure the paint is hard, and then just polish the spots in. When I have to do a touch up, I just give it a little 400, brush it on, scrape the edges to feather them, and polish it. No primer, no problem, don't have to worry about burning through.
All in all, you're plan of spraying would be way faster and easier I imagine. I only had a weekend to do it, and just did what I know.
I used cheap bondo to fair in small imperfections, and I don't care for it, I'll tell you that. I was in a hurry though, and boy does it go off fast! I'm going to paint my '49 pontiac next winter, and I'm going to use lead. It's so moist here on the coast, that I'm sure eventually the bondo will let go. Plus, it always post cures in the sun and shrinks further. I'm sure pros are better at it than me.
