AJ.
I have been informed by my local supplier of Vallejo Paints that it is possible to airbrush with the Model colour range of Vallejo paints, although I haven't tried it myself yet.
I was advised that the colour would need to thinned to a consistency suitable for airbushing using distilled water. You can also obtain a Vallejo thinner (524) although I believe this could be an expensive way of thinning the paint as it comes in the same size bottle as the paint.
If you go ahead and airbrush please post the results as I would be happy to read it.