PPSS...I damaged some of the alclad covering during handling, airbrushing with future did the trick, no tonal difference and nicely sealed...I learned from that..
My Iwata airbrush with 0.2 nozzle is too little to handle large surfaces, it took forever to cover the aircraft and as a consequence I applied too many layers, used 1 bottle of airframe alu...!!
Try to unscrew the head Cap and apply without it. Be careful of the airbrush needle because it is protruding from the nozzle and isn't protected fully. But you can spray much larger surfaces.