Sand the wall using a sanding buffer with a fine-grain sanding ring. This will smooth down any areas that are rough or uneven.
Wipe off the wall with a washcloth to remove any dust or debris.
Fill a paint tray with matte latex wall paint, then coat a paint roller in the paint.
Apply the matte latex paint over the entire wall, then allow the paint to dry for eight hours.
Apply a second layer of matte paint using the paint roller, then allow the paint to dry for another eight hours.
Fill a second paint tray with glossy opalescent latex paint. Place a ladder next to the wall, then climb the ladder to the top of the wall. Coat the end of a 4-inch flat paintbrush heavily into the opalescent paint.
Hold the paint-covered brush against the top edge of the wall with the bristles pointed down for two minutes. This causes the paint to drip off of the brush and down the wall. Repeat across the entire top edge of the wall to create glossy, opalescent "raindrops" falling down the wall. Allow the dripping paint to dry for eight hours.