When I am airbrushing I find that sometimes I get no paint coming out of the nozzle. If I shake the bottle around or open it up I get a whole bunch of spray then I have to close it down again. This happens in between passes (to flip model etc). I don't thick it's to thick because my first batch of paint was too watery, I added a bit more paint and voila it seemed better. I am using the Aztec 470 double action and enamels (humbrol). Could it be that the bottom of the container has a thicker consistency then the top portion? Any suggestions would be helpful. The AB is brand new 5x uses and I ma using a compressor that has 250 psi capabilities I usually use 25-30 but for fine nozzle 15. I found that ten I couldn’t get anything to come out (too thick maybe)?

Padrino, it certainly sounds like it's too thick...the paint that is. I use the same AB and spray through any and all the tips at no higher than 18psi. 15 - 16 psi average for me.
The paint when thinned should be the consistancy of say - lowfat milk. The paint should be evenly mixed - from top to bottom. If you let the paint sit for too long the pigments will settle in the bottom and cause the inconsistacy.
Also make sure your tips are cleaned well after each use. Just around the outside of the tip's nozzle paint will collect. Clean this with an old toothbrush or similar.

Do you use a filter on the end of your pickup tube? They sell little brass screens that fit over the end that will screen out any blobs and trash try one. And when done just remove the tube and drop into what ever is the solvent for paint used. I picked up a hair one time !! Really triped me out of how it got mixed in paint. Most likley cat