First step with moss is to pay attention to the surface / what the moss is growing on and location of the moss. heavy shade light shade along a road but brite. along a stream. on top of rocks in the woods or growing on sand, wood or compost.
for a vertical surface try using fabric for the roots to dig in as much as moss sets roots. If its going to be kept wet just rub a similar moss against the fabric . it will grow . and like jw said there's cocktails out there. i do like
@Jhn and keep tucking different mosses until one likes the area and takes hold. Out there
@combatwombat you probably won't have to work to hard to get it to take over. your not in the arid desert out there you'll probably be mofoing the moss in no time.
another plant i would concentrate on is FERNS. YOUR IN MOSS AND FERN HEAVEN OR HELL DEPENDS HOW YOU LOOK AT IT