Texture Painting in Blender for Absolute Beginners - Surfaced Studio

Blender Texture Painting with the Layer Painter addon [$]

A-Z Environment Design using Trim Sheets

ArtStation - Creating Advanced Trim Sheet Textures for Games - In-Depth Tutorial Course | Tutorials

FastTrackTutorials - Creating Advanced Trim Sheet Textures for Games - In-Depth Tutorial Course

Using Procedural Textures in Blender

Blender Procedural Texture Tutorial | BlenderNation Bazaar

Simple Procedural Textures