Read the directions. Then do it how you feel it will go together best! DPM are pretty easy and forgiving kits.
I use all kinds of paint. (you should see our collection of paints!!) Most of them I thin down with the appropriate thinning liquid. (water, thinner, alcohol etc) Even cheapo Walmart spray paint works just fine for some applications. Just be very, very careful and stingy with it! Floquil, Polyscale, some craft paints, some testors, etc, flat or shiny depending on the area to be painted. (dull cote or seal them when finished too) (just watch that you don't get any on the windows, if you do, consider them "weathered" because you won't get it off of them!) India ink & alcohol for some weathering. Other weathering depends on the color desired. I use any paint that I want to gain the weathered color desired. Again, thinned out ... alot.
I usually paint most of the structure BEFORE I build it. I touch up anything after it is assembled. Painting the inside with a dark gray or black looks better if you are going to light it. Room dividers look more relistic this way too. Oh, and after I put the windows in, I install curtains, shades, etc before putting it together too.
Thin, natural hair brushes for most of the painting. I don't like to airbrush much, but it does do a nice job when it is a big structure with lots to paint. Just tape behind the windows & doors so you don't get any overspray! You can buy canned air if you don't have a compressor. All kinds of masking type tape and thin, pinstripe tape works for some of the finer painting if you don't have a steady hand. (Like me!!)
Make sure you don't have any paint where you will be gluing things together. It makes a mess, trust me! I scrape any off with my knife or some thinning liquid if I get some on by mistake.
I also use a big lighted magnifying glass (and reading glasses) and one of those extra pair of hands. You'll need tweezers, clamps, files, toothpicks and many other things. I even have some dental picks for getting into the small, tight areas. CA glue, testors glue, etc and make sure you have the release liquid just in case.
Paper towels, old t-shirts, etc for blotting. (and for spills, I am famous for that one!)
Gosh, this list goes on and on and I didn't get it all down.
Most of all, have fun. It took time to gather all of these supplies and I am still learning and gathering!
DZ