I have just finished an article on how to get moss to grow in shady areas. On rocks, old fences, planters, etc.
You need a blender and add 1 cup of milk + 4Tbsp. of vinegar (buttermilk) add some moss you have found and blend all this together.
Paint it on the article you want moss to grow on and cover with clear plastic for 2 weeks. Spray every 3-4 days with a spray bottle with water. Remove plastic and water with a spray bottle and keep it moist until it takes hold. I am going to try it on some rocks and 2 planters under some trees where the sun never gets to.
Sounds like a fun project to try.