Brush or shake soil from a clump of living moss. Rinse it under cool running water to remove as much remaining soil as possible. Gently press the moss between your palms to remove excess water.
Add 1 part moss and 4 parts buttermilk or plain yogurt to a blender and blend thoroughly until the moss forms a thick soup.
Smear a thick coat of the moss soup onto a clay, stone or cement pot with your fingers. Apply it with a paintbrush if you want a more hands-off approach. Put moss in specific areas where you want it to grow on the pot, or coat the entire item with it.
Set the mossy pot in a plastic grocery bag and tie it shut loosely so air can circulate. Place it in a cool, semi-shady spot.
Mist the moss gently to moisten it thoroughly. Repeat at least daily for two weeks, keeping the plant moist. The moss will be well-established in about two weeks.
Water the moss enough to keep it from drying out completely.