If air brush some thing acrylic based and thin but as for spray paint my best bet would be the fabric spray paint . Unless you don't care about detail then regular spray paint will work . Use to put handstyles on shirts all the time they do fade but here is a video

 

Wow Thanks! Really interesting! Gonna have to start looking at airbrushes! Do you have advice on which ones to look at?

 

Actually you can still use One Shot oil based sign paint to paint on T-Shirts which will virtually eliminate the constant tip drying problems you get when spraying (water based) acrylics..the only draw back is that its toxic as fuck so you have to wear a full respirator.

And it's color fast..

 

I use an iwata hp-c airbrush, it’s great for automotive murals and graphics, but if you want finer detail you’ll need a micron brush. Gravity feed dual action is the way to go. Single action airbrushes are rubbish and Venturi feed brushes suck balls. A good entry level iwata airbrush will set you back around $350 Australian dollars. A good micron brush you’ll be looking at around $850 aud.