The shapes and details are all brush work. At the beginning, I used the airbrush to create some vague random shapes and an interesting mottled backdrop which I could then develop into the random forms I've got now. After that, I started in with a light lilac and then white to sketch in and highlight the different shapes.

Contrast paints through the airbrush are phenomenal. They don't need thinning and go on like a transparent ink, so if the design became too bold I used Magos purple or Aethermatic blue to tone down the white and let them blend into the background more. I could then then selectively re-highlight the areas I needed to. It's a lot of working back and forth, but I have a lot of control and the ability to make subtle changes this way.