Watercolor with Grease Pencil Tutorial - BlenderNation
Mini Tutorial: How to quickly create grease pencil outlines with nice variation in thickness/opacity for a bit more complex geometry by Luamono (details in the comments) : r/blender
Grease Pencil in Blender 2.8: how to draw a manga
How to draw in 3d space with GREASE PENCIL | Blender 2.9 ALPHA | Tutorial - YouTube
Color Like a Pro – Blending | Blending colored pencils, Colored pencil techniques, Pencil drawing tutorials