3/13 is a good size. Don't max out the pressure, just enough to get a good fan. This will reduce blowback and increase transfer efficiency.
Using the right paint is critical. There are a number of characteristics that vary product to product that make a huge difference.
Non-enamel paints will not block ie the paint will stick to itself if on two different touching surfaces. A good trim paint will block almost as soon as it is dry to the touch. In the past I have had horrible blocking issues with Valspar. Sherwin Solo Gloss is superb at blocking.
Layout. A good trim paint will lay out/flow very smooth even if the millage is low. Sherwin proclassic orange peels easily if put on too light, but runs like crazy if you put a touch too much on. Sherwin solo gloss flows very well and dries quickly. You should always be increasing the heat in your work area to deal with the moisture produce and to get the coating to set quickly. Turn up the heat and bring a couple shop lights.
Sandability. Some paints will sand off in a powder, others will peel off. Proclassic will sand, which is good because it always runs like a mofo. Solo will sand if you need too but you generally won't.