Bathroom ceiling repair
The spray with warm water trick works with popcorn ceilings IF they haven't been painted. Unpainted stipple (thinned joint compound) should scrape/sand off easily. Sounds like yours has been painted. As Paulie stated, it can be skim coated to a smooth finish. A better solution might be another layer of drywall with smooth finish. And perhaps it's time to upgrade the exhaust fan to a bigger unit....
If you can read this, thank a teacher. If you can read this in English, thank a soldier. Support our troops.