Wow, it’s been awhile. Life has really been smacking me around. On the airbrush front and ready to go airbrush paints. Basically the thinner the paint the lower the PSI. I’m not familiar with the Cobra but I’m fairly certain it’s a badger design. The Cobra, or more properly the Air Cobra, is a fine detail airbrush which makes it pretty finicky, a .2 needle is really small. That means at low PSIs, which is what you need for thin paint, it has to be really clean. Any kind of debris in there will make it spit at low PSIs. I usually work in the 10-12 range and as low as 8 as needed.
The Ammo by Mig airbrush paints are by far my favorites and they work pretty well right out of the bottle with a paint brush. Any paint will work through an airbrush if you thin it enough, it’s just a question of it being worth the effort. The PSI you work at defines how much thinning is required. That’s why there is no magic formula, depends on the paint and the PSI you are comfortable using.
I use a Renegade Velocity for detail work and a Badger Patriot for bigger stuff.