Thinning paint

All I can suggest is practice. Take an old build and use it for testing your various airbrush techniques upon. Experiment with your thinning ratios, air pressure and distances until you feel competent getting the thin lines that you desire. Using an actual old model helps because it gives you the angles and curves that you won't get using a spoon, piece of cardboard, or other such surface. 

Thanks Stik.  I Hope you are well.  It's going to take practice.  I have a couple practice pieces that I'll experiment on.  Maybe I'll start keeping a journal with ratios, distance, paints, etc for reference.  The great thing about this hobby is the many techniques that can be utilized.  This is one I'd like to learn.

I don't think you live to far away from Nationals.  You plan on going?  I'd bet one of your models could win.