Hi
Have used the following method with some success best on stone rather than wood.
Scrape off the mosses from rocks and put into a blender with buttermilk. Blend to a consistancy of thick cream.
Paint this mixture onto dampened rocks .Make sure they stay moist until new growth starts.
Had better luck on terracotta and no luck at all on wood.
i suppose it makes a big difference on the preferred substrate of the moss type either acidic or alkaline??
It does work though gary