Plenty of views, and no response
so I'll try and answer your question Hemi...
If you have the paint thinned properly, then I would suggest spraying at about 20 - 30psi. depending on the airbrush, and size of needle.
What type of compressor have you got, as that has an effect on pressure available, and consistant supply?
I have a few airbrush's, and when spraying let's say Tamiya acrylics, I will use the above pressure, unless I am after different effects.
If you want a textured finish, use a lower pressure, and spray a bit further away from the part you're painting.
Don't have the pressure too high or else the paint will tend to dry before it gets to the part, and also clog the end of the needle/tip on your airbrush, so you'll be constantly cleaning the tip.
As with all painting, practice until you get a feel for the type of paints you are favouring, and you'll soon get to a ratio that suits your needs.
Hope this helps.