Hi,

When I was younger, dad and I used to get moss that grew on the hard
wood in our garden and put it on the soil of the bonsai trees. Some of
it would take, but some would die off. If you want some moss on the
other tree, perhaps take a small patch from the tree that has some
(like when you buy turf for a new house) and plant it on the weeded
bonsai.

About the leaves - I was always told that cutting certain leaves in
half was a way of training a tree to grow small leaves. I think it
only works in some trees, as others will always have big leaves.