I haven't used the Freak Flex paints, but I have used their Accu Flex paints, which I assume are the same formulation. It's been a while since I used them, but as I recall I did end up thinning them slightly for air brushing, but much less than, say, Pollyscale or Testors. You may have different results depending on your airbrush, so experiment a little. I found that they airbrush well, but are too thin to cover effectively with a conventional brush, which made small touch-ups difficult.