Here's a way you can accelerate and establish a beautiful green moss cover over your garden rocks and concrete features. This method doesn't work well on resin statues and artificial landscape rocks.
First stir a fist size clump of porcelain clay into 3 cups of water to form a thin paste. You can usually get porcelain clay from local hobby shops.
Then combine the clay mixture with one cup of undiluted fish emulsion and one cup of fresh, shredded moss. Fish emulsion is a plant fertilizer made from whole fish. It’s usually available at retail nurseries and garden centers.
Mix everything together and paint it on your rocks and concrete objects with a paint brush. Keep things in the garden slightly moist by misting and taking care not to wash the mixture off.
Remember that moss grows naturally in patches, likes the North side of objects, and takes readily to cracks and crevices.
Use this formula in shady gardens and in moist locations and you can most probably have moss on your garden statues and landscape rocks in a few weeks.