I picked up a great little technique from the Neville Page Gnomon master class and thought I’d give it a try.
The process involves poly painting on a 3D plane in Z-Brush with symmetry turned on. When you first start to paint keep the Sub div level low on the poly plane. When you paint the brushstrokes look blurry and pixelated, don’t worry if it looks bad at this stage since it’s this lack of detail which provides the Rorschach effect and allows you to see possibilities you might not have thought of initially.
What I particularly like about this technique is how fast it is, as your brush stroke is mirrored while you work the design comes together much faster and since you’re working in a front view, you can focus purely on design.