1. Decide on the motive you want to paint. Carleen went for a portrait.
2. Draw the outlines of your portrait with graphite pencil and correct until you are happy with the result.
3. Re-draw the outlines of your portrait with markers. Carleen is using FW Mixed Media Markers filled with FW Ink Black with a chisel nib 1-3mm.
4. Once your outline is ready, set your airbrush on 30-40 PSI for ink, depending on the recommendations of your airbrush producer for ink.
5. To get used to your airbrush use a blank piece of paper and switch in-between bold thin lines. Paint some basic shapes such as hearts and try to switch the line thickness while painting.
6. Decide on the transparency of your colours. Daler-Rowney offers different inks ranging from Aquafine (transparent watercolour ink), FW Ink (semi-transparent ink) to System3 Ink (opaque ink) and load your airbrush
7. Start with filling up your portrait with the lighter colours and set shadows with a darker tone.
8. Make sure to clean your airbrush head with every new colour you use to guarantee colour brilliance and a good air flow.
9. Once your portrait is fill-up set black and white highlights for more depth and reflections.
10. Correct details with your markers and sign your artwork.

Congratulations you are done with your first airbrush portrait. Practice makes best, so stay creative and your skills with the airbrush will improve quickly. 
Most important, enjoy the process of creation!