How much airbrush thinner

I recently bought the testors single action airbrush, and have all of the Tamiya acrylic paints. When thinning this paint, how much thinner should I add? i've never done this before, thanks for the help

Start with 1 part thinner to 3 parts paint (25% thinner)
If that is not wet enough add thinner

:p

It tends to be easier to thin as you need to. Any ratio is really just a rough suggestion- how much thinning is needed varies alot with temperature of paint, temp of ambient air, ambient humidity, air pressure, flat vs gloss, age of paint, phase of moon, blood alcohol, etc.

When I spray acrylics (whic is nearly always, cuz they work great, and there's nothing easier), I have a bottle of 'thinner' premixed in an old contact lens saline bottle. Any plastic dropper type bottle will do. The thinner is 3 parts distilled water, and one part isopropyl alcohol. Put a bit of paint into the color cup, add a couple of drops of thinner solution. Swirl gently. Spray onto 3x5 index card. Not thin enough? add a touch more. Spray until hearts content. When done spraying, just clean with Windex (glass cleaner). I use 4/1 paint/thinner as a place to start, but always test spray, and adjust as needed.

good luck