Part I of.... many.
I figured I'd do a step by step of one piece while incorporating little techniques for each part. This part includes:
Trees/BarkHINT HINT HINT
I couldn't find a place for this in the tutorial, but it is a HUGE help: When you have the brush tool, press the Alt button. While you're holding it, the Eyedrop tool comes up. Click your new color, then let go of the button. It keeps you from having to keep switching back and forth between colors.
Sorry for the size. And sorry if it feels haphazard. D: May edit this laaater.
Feel free to ask questions!
Other Tutorials: Part I -- Trees, Clouds, and Painting Technique
Part II: Marble, Stone, and Cracks
Part III: Skin and Face
Part IV: Details, and Clothes
Part V: HairHow to Learn from Tracing Final Image