I've used three Krylon colors decanted and airbrushed. Not a lot but have used them. A bright yellow, Sunrise Yellow I think, gloss black and Crystal Clear. I thinned all of them with lacquer thinner. I don't measure, I just add thinner till I think it's right and try it. Probably won't have to go as high as 50 - 50 or 1 - 1, however you look at it. And you probably already know this but I'll say it anyway, be sure to let the paint set open for a while after decanting so the propellant can gas out. I got in the habit of letting them set for a day. If you need some in a hurry then stir it gently till you stop getting bubbles and the bottle/jar doesn't cool. But whatever you do, don't screw the cap on and shake them till they have gassed out. 
Don't ask...
Tony