I use a Grex gravity-fed dual-action airbrush. My typical practice is to put some thinner in the paint cup using a pipette and then pour the paint (I typically use Tamiya acrylics) directly into the color cup. However, for most small paint jobs I end-up with way more paint in the cup than I need. Also, the ratio of thinner to paint is pretty imprecise. Then when I am done painting, I have a lot a paint to pour back in the bottle which still leaves quite a bit of paint in the color cup to clean-up.
I guess I could be much more precise and use less paint if I extracted paint from the bottle using a pipette. Though then you have to throw-away or clean the pipette. Throwing away the pipette seems wasteful and cleaning the pipette seems like it would be a pain. Though maybe cleaning the pipette is easier than I think.
With the Valero sqeeze bottles you can use just the amount of paint you want. Has anyone purchased squeeze bottles and transferred properly thinned paint to that?