Hey, nice work Daniel.
The hardest thing about sketching is just getting the first one down. The second becomes pig headed determination,
You'll find your technique will continue to develop to your own style, and the materials you use too will change until you find what best works for you.
Grabbing the bull by the horns is the only difficult part. Run with it, mate.
By the way, I too find depicting mountain ranges very tricky. They are so detailed, with so many nooks and crannies, and just so much of it. It is just overwhelming the amount of detail.