If the moss used was harvested from a full sun site, meaning the species of moss used normally grows in full sun, then the tree with fresh moss planting should immediately go back into full sun. Humidity is key to getting moss to take. Outdoors, in summer, in most areas except desert regions, humidity will almost always be above 50%, which will be enough to get the moss going. Keep the tree on its normal watering schedule. Moss is real tolerant of drying between watering, as long as humidity is moderate to high. (anything above 50%).