Daniel, as far as I'm aware the Model Air range are pre-thinned ready for spraying.
Don't use an alcohol based thinner as these paints don't react well, as you have already found out. Just use distilled water, as i found that works fine.
The other thing I found was to ensure that the surface being painted has been properly primed, I didn't realise this the first time I used them, and the paint just shredded each time I handled the model.
From a purely personal perspective, I didn't find them any better than Gunze, but then others swear by them.
Karl