Frankly the metallic colors in the Vallejo Air line are better, they actually have aluminum powder added to them to give them that metallic look, and lots of variety for colors as well.

And while they are Vallejo Air...they can be brush painted as well very nicely.

m1ks.....dunno what to say, I have been using Vallejo for 7 or 8 years, and have never had a problem thinning the Model Color to airbrush or brush on. I have used everything under the sun, and find nothing better out there. Just seems you had a bad experience and not indicative to the brand of paint. It is possible you got a bad bottle, but for the most part Vallejo Model Color brush paints circles around most brands. And while I haven't delved into the meat of the Air line, the few I have used work beautifully.