The bust itself consists of three parts (glass hood, body/head and outlines) each of which is made out of different materials. I painted the material for the body and head manually in Substance Painter. After carefully studying the artwork by Ben Harvey, I started painting the head layer by layer. The great thing about working with Substance Painter was that I could have a layer for each color. This allowed me to work nondestructive and precise. I used some handcrafted alphas alongside with the default watercolor brushes in Substance Painter.
In order to create a convincing outline I used the “inverted hull method”. I duplicated the hull a few times to create multiple meshes for the outlines. For each outline mesh I had to create a separate second material slot. For this material I painted for each outline a separate image texture, where stamped some random brushstrokes.
Then I joined all meshes that were sharing the same first material (body or hood) and added the solidify modifier. The “inverted hull method” with the solidify modifier is very flexible, and you can achieve vastly different results with it in order to fit your style or liking. The most important settings are the flipped normals checkbox, the thickness and the clamp slider. Everything else is optional. But in this project I also used vertex groups to tweak the details and the thickness of the individual outlines manually. This allowed me to create wobbly outlines, which helped create a convincing hand painted look.