Painting the sky!???!!
Consider buying the stars that glow-in-the-dark after the light has been on for a while. It's really neat! You may have to hunt around for them. Search the WEB or visit a store like Edmund's Scientific. Talk to other parents too as well as the folks in your local paint stores.
You could cut out various sized stars, tape them to the ceiling, then paint. Be sure to use Painter's Masking Tape; NOT any other kind of tape no matter what it's called.
My best to ya and hope this helps.
Jay J -MOderator
PS: I know these glow-stars are made because they were ALL over one of the bedroom's ceiling. It was called the Grateful Dead Room. !!!