Hi Mario,
I use alot of craft paints similar to the Americana brand, even have the odd bottle in my pile o' paints. Yes they are cheaper, and some brands are better than others. If thinned down enough, they can be airbrushed, and when using a brush to paint, it will take 2-3 coats to get coverage, as I find the paints a bit translucent. Give them a try and see how you like them, I actually use them quite a bit to paint the cammo on my German figure uniforms.