Remove the water-stained tiles from the false ceiling. Lay the tiles on a worktable or on the floor.
Apply oil-based primer to the stained ceiling tiles with a roller. Let this dry for two to four hours, until the surface is no longer tacky to the touch.
Apply the first coat of oil-based ceiling paint. Apply a thin coat with a roller over the primed area. Let this coat dry for two to four hours.
Apply another coat of ceiling paint using a roller, to ensure that the stain will not seep back through. Let this dry completely.
Replace the tiles into the ceiling.