First you get some Elmer’s glue and thin it down with water. Then you paint that on the wall. While it’s still wet, fill a straw with glitter and gently blow it on the wall. You can use as little or as much as you want. Leave it alone until completely dry and then go over it with a feather duster to remove the loose glitter.
This is how they do it for stage sets. Don’t put any coating on it at all, polyurethane will dull the glitter and it won’t be sparkley anymore. Happy Glittering….