I use a terrain generator built into Blender called "ANT Landscape".
It's not as complex or detailed as something like Terragen or World Machine, but it gets the job done.
I have a shitty tutorial on Youtube that I think covers it. It's a bit old as far as my style goes, but it's basic enough to understand.https://www.youtube.com/watch?v=pu7DNU21X3c
Not that I really reccommend watching it though. I'm not the best teacher, and the video quality is mashed potatoes.
As for translating it to pencil and paper, I'm not entirely sure.
This kind of art thrives on computer screens because of the inherent luminescence given off by them. It's kind of a hard thing to replicate.
But then again, there could be a really great handmade quality about it that transfers really well with pencil.>>6420858
This one I did seems like it would work in pencil well enough. As long as there's enough variation to really work, I think it's fine.
And if you add color, the palette alone can push an image into the style.
Check out Patrick Nagel's work for some inspiration. Although there's color, there's a lot of heavy blacks used, and it still conveys the era quite well. I think a mix of something like that with a more traditional approach could help out.http://www.patricknagel.com/gallery.html
Hopefully this helps a bit. Drawing is a ton of fun, and a great help for this sort of thing.
I'd really like to see what you could do with this style in pencil. It could be really interesting.
(Sorry for the long response)