We just took popcorn ceiling off and want to know a good primer and paint to make a smooth ceiling.
The solution depends on how much texture remains on your ceiling. Generally when textures are removed, imperfections in the substrate remain. I am not aware of any coating which, in one application, will hide this.
Our practice is to apply one or more coats of drywall joint compound to smooth the rough spots, sanding between coats. This is a dusty process, but the best method I have found. After smoothing the surface, prime and finish.