I've been wanting to do this on my back wall as well. From what I've seen on directions, the best technique is to spread the moss around the in small patches across the entire mesh. It seems to grow a little better and you should see faster results.
Looks like you'll have to get some more or do what Steven_P says or incubate it in a dedicated container.
What kind of mesh did you use? I've been looking at http://www.papermart.com/Product%20P...tGroupID=19024