As requested -- a detailed tutorial on using blending modes in Photoshop!
For more skilled artists who know about this stuff, there are some good tricks in here about removing undesired line work and artifacts using blending modes.
Needed to practice my landscapes more -- it's amazing how out of touch your landscape skills get when you've been doing nothing but character art for a month!
Studying Ireland helps! I looked at photos of Strath Mor to get me inspired to do this study. Learned a lot about how to set up realistic skies in 3D space.