Hi. I'm VERY new to this thing, bought my 1st airbrush a few...

Hi. I'm VERY new to this thing, bought my 1st airbrush a few days back, have been working with just traditional brushes up until now. Got an airbrush cos shading murals with brushes is painful.
The first time I tried the brush, no paint came out, only air, but I twisted the cup around a few times and it started spraying it out. terrible flow though, and then it stopped, though the paint wasn't finished. it was thin enough for sure, even got some spidering it was that thin. Ever since, its not sprayed out ANY paint. I unscrewed the nozzle cap and needle cover, there seems to be no clog anywhere. when i try to clean it out with water, closing the nozzle with my finger, it backflushes properly..i assume that means the pathways are clear? but im new to this so i could be wrong. i've tried every possible angle with the cup. theres only 180 degrees it can turn thru anyway and stil work right? i called up the store they do no demos. he said hel replace the airbrush for me in two days but that is really not the point is it. please help someone. im going nuts here.