From my experience with Humbrol paint in these dropper bottles, is there is a big issue with consistency of the paint. The first one I got, I had no issues with airbrushing straight from the bottle. Second one too thick, so watered it down. The next four bottles all different viscosity. Having said that they are very workable with a paint brush, but I personally did't purchase them for the use with a brush. Maybe they have used what stock they had left from the pots to put in the dropper bottles, who knows but the manufacturer and maybe Humbrol didn't know the manufacturer was doing this. I personal feel there is a big QA problem some where. Any paint can be used through an airbrush, it just needs to be thinned if needed.