I'm often asked what I use in my Iwata airbrush and, after trying several different products, find that Liquitex Acrylic Ink is a definite favourite. It's permanent and works beautifully with the Liquitex Heavy Body acrylics I use plus it is easy to clean out my airbrush once I'm finished working...which has to be fairly immediate so that the parts don't become clogged with dried paint. I make my own airbrush cleaning solution, though it is available to purchase and can also be used to thin acrylics for use in an airbrush.
I typically set all of my materials up before filling the reservoir which is attached to the bottom of my airbrush (versus a gravity feed from the top)...my canvases and stencils are selected and set up as well as attaching the airbrush to the airhose & compressor so that the ink doesn't sit in the airbrush longer than absolutely necessary. Then I fill the container with the selected ink, turn on my compressor and utilize my dual-action airbrush (the trigger controls both the amount of paint and air is expelled at once). As soon as I've finished, I take my tools apart and rinse all the airbrush parts in hot water then run the cleaning solution through it.
Since I'm not a huge fan of major clean up while I work, I'm surprised how much I love my airbrush as it is rather finnicky and time-consuming. But I really do. And my air compressor is very loud but I do love how small it is. I don't use it like a traditional airbrush artist does to create images, but rather to add interest to my backgrounds. It's been wonderful as spray paint cans made me uncomfortable because of their impact on the environment. Plus this uses so much less paint.
Airbrush Cleaning Solution (for water soluble paint):
2/3 distilled water
1/3 isopropyl alcohol
1 drop glycerin per 50 ml