To midpwrguy's comments that the auto paints are "simple". This is true if you are careful about setup, prep, temp/humidity conditions and mixing. The shooting is remarkably easy with such good product and good guns. Like anything else, though, it's all the other stuff that makes it a hassle.
Many airbrush artists outsource the clear coating to autobody shops, as they can use safer products for base and layered color coats.
Honestly, I don't find shooting outside an ideal solution to the problems that isocyanate fumes present. First, you can't control where those fumes are going, the breeze could blow it right into your face. Second, especially here in dry, dusty Colorado, getting dust-free results in an uncontrolled outdoor environment is not a good bet.
As for HOK products, they make both 1 and 2-part formulations. It's the 2-part stuff (with the isocyanate hardeners) - e.g. the clear coats - that demand special attention. The "regular" 1-part paints, including many of their base and regular color coats can be safely handled with normal respirators and normal ventilation conditions. So, if you're willing to pony up the money for their products, I say go for it.
