What I do, is start with the biggest bricks you are going to use and stay in a grid.
Sketch the rough outline and where everything will go.
Then use one smaller size bricks and make the shape a bit smoother.
Always stay in grid, you don't want to see vertical holes in the mountain because you misplaced a brick by 1.
Keep making your brick size smaller and smoothing the shape.
Be sure to use the double stacked '8 cubes' at the end instead of the normal '8 cubes'.
Then you can use the steep 8 slopes so a player can't climb the mountain.
A player can run up the normal steep slopes, so be sure to use as many slanted steep slopes as possible.
Edit: Yeah yeah I hear ya, it's grid not grit
If anyone wants to correct me with the correct terminology, that would be great