Experience! Seriously though, leave the air pressure up as normal for good atomization . I don't know what gun you have but the guage should be about 25psi if you are using HVLP fittings. You can dial the pressure down a bit of you like. Dial in the fan just a little from full fan. Adjust the trigger to about 1/2 way. Again I don't know what kind of gun you are using but the trigger adjustment is usually a knob with a threaded stop nut of sorts. That will regulate the flow of paint and the tighter fan pattern will get the paint down low into the hard to reach area. I like to get the hard to reach area first. Then while its still wet lay a coat on the rest of the panel. Don't forget to open the fan back up along with the trigger. That way you don't get dry areas in the crevices or dry areas elsewhere if you do the crevices last. It's harder to explain rather than just doing it.
