How's this for overkill: the mountains have 5 layers that build up to the effect from the earlier test image.

Basic Outline (upside down V and a squiggly line going down the middle for the light/dark transition area)
Dark Outline, where I darken the edges of the darkside of the mountain
Dark Shading, where I fill in the shadowed portion
Light Detail, where I add in crevasses/etc and give it some texture on the light side
Light Shadows, where I shade the lightside details

And somewhere in there (usually the light detail and light shadows) i throw some bits down along the valleys and lower slopes in the space between one mountain and another to fill in smaller spaces. Some of the larger spaces will be dealt with on the Hill layer groups

There's a mini tutorial somewhere in the Tutorials forum that introduced me to the style.. I added my own twist by separating each step to it's own layer. I can't find it right now though, but I'll take another peek in a bit. I saved the png attachment and keep it open on the second monitor while I work for ease of reference