This is actually my first art question ask ever, so I’ll do my best! You’re actually pretty much spot on with the brush thing. Good eye. For a lot of my recent work I just stipple and pattern all over using the basic Photoshop brush, 100% opacity. If I feel some areas need a more painterly treatment or texture, and I’ll hit up my Kyle T. Webster brushes.
As for color, I generally scribble over my sketch with a rough palette to begin. I look at a disturbing amount of old landscape paintings and prints, so that’s often where my palette inspiration comes from. I’ll probably tweak the colors from my initial idea once I refine the rough shapes. The details involve a lot of eyeballing and spontaneous decisions, although I’ll usually end up working in muted versions of my original colors into the blocked shapes to fill out my color scheme.
There’s a fair amount of trial and error involved, but color is my favorite thing to study and play with, so it’s a good time. :)
Hope that answered your questions! I may try to post more process shots in the future if folks are interested.