Purchase ceiling glitter from a paint store. For a subtle effect, choose clear or white glitter. Colored glitter may look gaudy and is best reserved for children’s play rooms, if used at all. Do not use standard craft glitter, which will sink into paint, wear out quickly and make a mess.
Vacuum the ceiling thoroughly, using a brush attachment to avoid scraping off any popcorn texture. Popcorn ceilings are notorious for trapping dust and dirt, both of which will prevent paint and clear coat adhesion.
Apply oil-based paint or clear coat to the ceiling using a long-nap roller. If you are using paint, choose a color that matches the ceiling's original paint as it is difficult to completely cover a popcorn ceiling. If your ceiling already has a significant amount of glitter on it, choose clear coat since opaque paint looks unattractive when applied over pieces of glitter.
Fill your gun with glitter and spray it evenly and sparingly over the wet ceiling.