This particular mini was blended in layers w a brush. But others I have done use an airbrush. I actually like to rough in shadows, highlights and mids and go in w an airbrush with about an 8 to 1 or even 10 to 1 ratio of thinner to paint. Then w very low pressure spray to blend. It’s not a super forgiving technique though. The liquid is so thin that you can potentially blast what looks like water everywhere. This technique is used by Sergio Calvo. Who I have done tutorials and gotten feedback from in the past. Go check out his youtube vids on airbrush use. Pretty great .