There's a liquid called BIX paint stripper. It's caustic, toxic, you name
it, so wear gloves and don't breathe vapors. Home depot; a few bucks. It
breaks down the bonding agents in paints (even old, bristle brushes coated
in dried oil paints). Take your air brush apart, put the pieces in a glass
jar, and pour in enough stripper to cover the pieces. Let sit for an hour.
Then with gloved hands and tools, pull out the pieces and flush thoroughly
with lots of water. Fire up the airbrush immediately, while any trapped
paint inside is still soft, and blow the innards clean!
This stripper stuff also saved about $300 worth of old, oil painting brushes
I was told to throw out by a painting instructor. Now she keeps her old
brushes for the day she "restores" them all at once. (For bristle brushes,
oil them a little afterwards, to restore suppleness to the bristle
fibers...)
Hope this tip saves everyone a little money.
Dan