I have always felt that dry-brushing is not truly a separate technique but merely the extreme point in brushing. The effect of brushing paint varies in an almost continuous manner from a brush completely saturated with paint, to a different look when lean of paint, to the extreme of an almost completely dry brush.
For instance, with either a brush or an airbrush, you can get gloss paint to look semi-gloss by putting it on in a light, dry coat, or flat paint to look semi-gloss by putting it on very heavy and wet.
And the original point by Tankerbuilder about artists using it is a good one. I tried both oil and acrylic painting many years ago as an attempt at art, and I know the skills that I learned in painting DO carry over to painting models. For instance, I learned to mix paint to get the colors I wanted, a nice skill when I don't want to worry about searching all the hobby shops in the area to find a rare color.