Amano used to blenderize moss into a paste and paint it on everything then grow it above water until there's a half an inch or so of even strong growth, then flood it.

Tom Barr prefers to use gen cyanoacrylate, which if you mix the dust that comes from expensive aquarium dirt (or regular beach sand) then it will dr brown instead.

Purbanta's method is to chop the moss, glue it on wood/rock/substrate surface, then flood it right away. It makes the moss grows more evenly and beautifully from the start. You don't need a lot of moss to cover a very large area too.