Actual propagation has proven more of a problem. Leucobryum , Racomitrium , Dicranoweisia . My success in the field with test samples has been non-existent. Suggestions have included possible dusting of powdered sulfur over soil to increase acidity - about 2.5 lbs. Fertilizer applied to mosses beefs them up like steroid athletes.
Trace elements are okay, but, again, no lime.
Watering as frequently as wanted is said to be okay, except for Racomitrium , which prefers to sleep dry in droughty weather. It never needs watering, not even when newly transplanted. Watering, especially in dry weather, can actually cause fungus infection. Medium seems to work, the manufacturer says the gel remains effective up to 5 years, after which it biodegrades. The missing element in implementing living moss roofs in the Pacific Northwest at this time is a process to initiate timely and uniform moss growth on new roofs.