3D Artist lassyla recently shared a tutorial on the EEVEE shader she uses for most of her Blender art, which is fully procedural, and despite the hand-painted look, there's no actual hand-painting involved. Noise plays a big role, and lassyla's video has a section explaining how it works, so even if you've been working with stylized shaders for a while, you might still pick up a few interesting tricks.
The artist also published the shader along with a demo scene where you can see it in action. It's available as a pay-what-you-want download, and lassyla asks that you tag her if you use it in your own projects so she can check them out.
