Spray distance, you might be holding the gun too far from the surface. I used to do that. Retarder can help orange peel. Test pattern. test pattern. You know. How hot is your painting room? For a while everything I painted had orange peel. My paint room is near the roof of my house, often painting during the summer. Guess what. Figuring that out took a couple of years. I have never been able to spray Brodak dope without a splash or two of retarder, same with Sig. Adding extra thinner makes it worse, causing the paint to dry faster. Painting with the temperature on the chilly side usually helps the paint level out. These days, if I paint in the summer, I turn the air conditioner on high for an hour. Go into the room, open my vent windows, turn on the vent fans, mix paint and spray. Usually everything stays chilled long enough so that the paint goes on o.k. The weather-- humidity, barometric pressure(?), temperature (of course) all effect the flow of lacquer (dope) and perhaps other paints (haven't used them much). So, I don't take a given paint mix for granted. Test pattern (that again) when using paint mixed up the day or week before. Don't be surprised if the neat flowing mix of one day doesn't work the next. Then there are the subtle techniques that are oh so difficult to describe. Such as fogging a first coat followed by a wet coat soon after. I remember asking an experience spray painter about putting on a first coat, how many passes back and forth etc. The poor follow started yelling and screaming at me. Made me think the fog of spray paint resembles the fog of war.