cleaners

Most acrylics can be cleaned using Windex, the kind with ammonia, or an equivalent window cleaner that contains ammonia. A 50% solution of Simple Green is also highly effective. I use either Windex or a mixture of half Windex, one quarter Simple Green, and one quarter water (sometimes called "Magic.")

You should clean your airbrush immediately after you finish painting. For short term, rinse or wipe any remaining paint from the cup. Then run Windex or "Magic" through the brush, backflushing occasionally. Do this twice. Then rinse with distilled or deionized water.

For long term storage (more than a few days) tear down the airbrush to make sure it is completely clean. 

With acrylics you can use Windex with Ammonia, Simple Green or any alcohol and ammonia based cleaner. I use ZEP brand myself. A gallon jug was about $9. It lasts a long time.

With enamels or lacquers you are stuck buying their specific thinners to clean with. I don't use those, but the actual steps for cleaning are probably very similar to what I do with the acrylics.

I use only acrylics (Tamiya) and never use their thinner to clean with. I also only buy the thinner in the 250ml bottle.

My cleaning regiment (Badger 100LG, 150 or 200-20) is pretty simple. First off good preparation makes the chore easy. 

edit I see Ross has beat me to the punch again, by being far less "wordy"! /edit

I have two recycled containers I use for cleaning. One is a large peanut butter jar I store "dirty" cleaner in. I use this for soaking off bad paint jobs and for cleaning color cups and bottles for my siphon fed airbrushes. The other is a milk jug I have cut an "X" slit halfway down. I use this one for the actual cleaning of the airbrush. I insert the tip of the airbrush into the slit and spray leftover paint and cleaner into it, which I then transfer to the storage jar when completed. I also keep a squeeze bottle full of cleaner, as well as another full of distilled water (more on this later), as well as airbrush lube.

If I'm using the siphon fed brushes I drop the cups or bottles into the jar with the used cleaner to soak while dealing with the airbrushes. I spray an ounce of new cleaner through the airbrush using a spare siphon bottle, and back flush by holding a soft cloth against the tip of the airbrush while carefully letting some air run through the brush. This makes sure that the siphon tube is flushed. I then pull the bottle of and swab out the tip (pulling back the needle)and siphon tube with a Q-tip. Then I spray about another ounce of cleaner through, followed by a half ounce of the distilled water. Pull the needle to make sure no paint is left on it, lube the front half of the needle with the airbrush lube and tuck into it's bed. Then I deal with the bottles and color cups, also washing off with distilled water. 

A gravity fed brush is dealt with slightly differently. Here I put a small amount of cleaner into the cup, swab out the majority of paint with a (used) Q-tip. Then it's the same regimen as above. Clean, back flush, clean and flush with distilled water, pull needle and lube. I also put a thin film of lube in the color cups. It seems to help prevent paint from drying on.

I use distilled water to prevent mineral buildup on the inside of the brush. Once a month or so I do a complete breakdown to clean every component and lube up the brush.

Following a similar regimen will ensure your brush is always spotlessly clean and will keep it in good tune for years of service. 

Triarius wrote:

Most acrylics can be cleaned using Windex, the kind with ammonia, or an equivalent window cleaner that contains ammonia. A 50% solution of Simple Green is also highly effective. I use either Windex or a mixture of half Windex, one quarter Simple Green, and one quarter water (sometimes called "Magic.") You should clean your airbrush immediately after you finish painting. For short term, rinse or wipe any remaining paint from the cup. Then run Windex or "Magic" through the brush, backflushing occasionally. Do this twice. Then rinse with distilled or deionized water. For long term storage (more than a few days) tear down the airbrush to make sure it is completely clean.

Much of that sounds vaguely familiar.