Since you're still in the planning stages, you might be interested in this article to grow your moss.
How to Make Moss Grow With Milk | Home Guides | SF Gate Basically what you do is to take a large clump of moss and put it in a blender with some Buttermilk. When you get a watery slurry, use a clean paint brush to brush it on the surfaces you want the moss to grow on. I've seen it work before and if you give the moss what it needs (shade and some moisture) it should work great, especially if you have some rocks you want to have moss grow on. Good luck.
Threaded Mode