I suspect I am not alone in discovering the amazing/dreaded airbrush via Giger. In his hands the tool was a magic wand capable of the most astonishing feats of photo-realism. I was a keen artist at a young age and, inspired by the look, read a great deal about airbrushes and the associated techniques. This was in the late 80s and early 90s which transpired to be the twilight of the airbrush's dominance.
In the late 90s digital would rise to become the weapon of choice. Digital, especially when combined with the now ubiquitous stylus, offers a similar toolset without all the faff and hassle of the airbrush. And much faff and hassle there is. Airbrushes are expensive, temperamental, dirty and noisy beasts. It takes a degree of patience, skill and wealth to persist with them. Consequently, they were often the mark of a truly professional designer or illustrator. Today airbrushes are predominantly used by the likes of modellers and muralists who have to work on a physical surface.
There are a hard-core of enthusiast artists who continue to use the tool for illustration. I stumbled across the video below showing one of them at work. The Frenchmen Hubert de Lartigue is a stunning portrait painter whose efforts remind us how great the airbrush can be. The video below is a great overview of the often complex techniques used to paint a portrait. The result typifies the airbrush's strengths - a kind of hyper-reality with a touch of real paintbrush strokes to remind you that you are, indeed, looking at a hand-crafted painting.
His work is wonderful, but I must confess I am not (nor, I suspect, will I ever be) ready to invest in an airbrush studio over and above my beloved iMac.