I made this painting to celebrate 1k followers on insta!
I also put the process + notes in my cubebrush store for free http://cbr.sh/qj01mz
I hope it can be useful!
First I use a square brush for larger areas with low opacity, then a mix of this brush + airbrush + a textured blender for radial shading and square brush again for hard edges hope it was useful. If you use CSP my brushes are for sale, while when I paint in Photoshop I use the Craig Mullins brush pack