Seeking advice on painting mountains

Hello all,

This has been eating my lunch all week.  I'm trying to paint some snowy mountains in the distance, and it's turning out to be far more difficult that I anticipated.

I've managed to paint the basic shape of the mountain range, and the rough dark/light areas... when it comes to the details though, things go off the rails...

What I've tried:

I create a layer on top of it, and dab wet oil brush light color over the area.  Then ive used a smear tool  (coarse and non) to kind of smudge it around (with Pick Up Underlying Color ON)  and it's... 'ok' i guess, but not what i want.

Ive tried using a pencil tool, to create random jagged lines and bright spots...  again, it looks 'ok'...

I've gone and watched actual oil painting tutorials, but they basically rely on their tools to create the randomness of the mountain face... like this one guy used a loaded pallet knife to create these awesome bright highlights... using Painter's pallet knife though, doesn't do anything close to this.  

Could any of you suggest some brushes/techniques i might experiment with, to try to create the 'random rock' look?  I do NOT want to just import some existing "rock" brush and dab it on there and call it a day... i'm trying to actually paint it myself.

Any advice would be appreciated!