[Painting]Thinning paints for airbrush?

My Vallejo paints just came in, including Russian Green.

I have set of GHQ T34s I would like to spray.  I'm using
the testors POS plastic clip onto the can airbrush, hey,
it works.

What I don't know is how much you need to thin the Vallejo
paints.  I've been using Testors stuff straight.  Anyone
have any advice?  I'd go the experimental route but at
15ml to the bottle I would prefer not to waste much.