I have a scene and I want to make both ground cover and sky clouds...Looking for some suggestions, tutorials, etc...

The scale of the scene is a mountainous area, roughly 6km around...though I dont want 100% coverage...the ground clouds would be below peak levels in the valleys.

I resist using Hypervoxels because of the blobbiness. I dont want to use a poly based object because its a pain to get soft edges.

Ive tried a VBO, but at that scale I need a ton of particles, which brings LW to its knees. Ive tried a straight volumetric object, but there's no option to assign a particle object to define its shape, distribution, etc.

Even a tutorial on using AE to create them in 3d and doing it all there would be fine.