Find two handfuls of soft moss. Look for it growing in shady patches of lawn, on tree trunks and in woodland areas. Remove as much soil as possible from the underside of the moss, as well as any pebbles, sticks or other debris.
Place the moss, two cups of buttermilk and 3 oz. of potter's clay into a blender jar. Put the lid on the blender jar and blend the mixture until it is thick and soupy.
Spray the surface of your rock or piece of wood with water. Then, using a paintbrush, coat the entire surface with the moss mixture.
Check on the moss daily and spray it lightly with a fine mist of water to keep the moss mixture moist. A mossy texture should appear within 2 to 3 weeks.