Both are easily achievable with the airbrush but utilize two completely different types of techniques. Stippled sprays are used to keep the object matte and to give it texture. A sheet of steel can be developed with a vignette of blue sprayed in a freehand manner from one side of the object to the other. The natural dot pattern of the airbrush lends to the feel of the steel surface. Stippling can be accomplished in two different ways.
Some airbrushes are adaptable to stippling tips or the tips are removed to spray larger dots.
The unique ability of the airbrush as a tool to depict the realism of a shiny metallic surface is well known. The key to achieving this is to think in terms of painting what is being reflected from within the object, rather than trying to paint only the object's surface. No matter what the shape or object is, to make it appear shiny, it must reflect its environment. To the surprise of some, you cannot make an object resemble chrome simply by airbrushing it silver. As an example, draw a square on a sheet of paper and paint a vignette of blue going from light to dark, top to bottom.