This is a post from the Internet Bonsai Club By Marcus Watts from the UK about mossing your trees to get them ready for a show.
stage one begins with a food blender / processor – I have the old one for jobs like this 
fill it with sphagnum moss – this is fresh moss collected in the autumn, chop it up very fine, dried orchid quality sphagnum works well also but you need to add some water.
once you have enough add water to make a sloppy moss soup
start adding the soup to the pot. The water drains through and you get a nice even and smooth layer of very fine sphagnum moss
Now you add the preferred top layer of moss, pressing it down into the moist under layer. This holds each piece in place as well as providing moisture from underneath. Doing this keeps the moss looking really fresh and the tree benefits too from the added humidity. I wanted a solid moss finish rather than patches here and there but made it from different sizes, colours and types of moss. This gives an interesting surface with several textures.
job done. Finally i added a piece of netting to the top to keep the birds from ripping it all off
Midwest Bonsai Society 
Great article, great format, and thanks for the photos in both of the August 7 posts!
Thanks for stopping by.
And how were the pads of moss created?
In this case they were collected from a shaded area of his roof. It is always a good idea to keep your eyes out for places near you where moss grows so you can collect it when needed. I have areas in my yard where it grows well, but I also watch for nice patches wherever I go.
I collect it too – just wondered if he’d discovered some magical way of growing it himself. 🙂
Over the past few year I have attempted to grow moss in various ways and to some degree it has worked, but moss can be very fickle. I still find that I can never get it to as well as does in it natural spots.