Ding ding ding, we have a winner……..right there is the secret to successful airbrushing. Keep trying until it works FOR YOU.I know I haven't been doing this very long. But!! I always found getting the thinning thing a bit of a nightmare. Now I mix enough thinning agent with colour using a brush to mix the paint. When the mix drips from the brush I deem the mix ready. It's not a hard fast X drops of this and x drops of that. So far my unscientific method seems to be working for me. I keep the pressure low(ish) 15-20 psi.
Whatever others do is just your starting point. You will gradually modify that advice (more thinner, more or less paint, a drop of flow aid, different pressure, whatever) until the airbrush works the way you want it to.
Airbrushing is a strange beast. Eventually, through trial and error, almost everyone gets it to work with whatever paint and thinner they’ve settled on. The weird thing is that almost everyone’s technique varies from everybody else’s, but they all end up with good results. I bet that (god forbid) we were all lined up side by side, every one of us would have their own unique way of preparing paint and spraying a model…..and all the models would come out fine.