Hey Steve!
If you take off the protective cap, then grab the air hose with one hand and kink it, like stopping the water flow in a garden hose. Then pulse the trigger on your airbrush, play around with letting a little and a lot of air flow through - that's what stippling is.
If you want a paint splatter effect then either add the colors you want underneath, then create a paint drop stencil and spray black over it, or spray down quite a few layers of different colors, then apply your black paint and quickly squirt a little reducer/ windex over the paint and soak up the excess with a clean cloth or rag. Just don't drag it across the artwork!
Best of luck!