What is your ceiling composed of? How large of stained area? My guess is either the leak is not fully stopped or there was just a lot of moisture above the ceiling and it all needs to dry out before any stains stop forming.
First of all need to know whether the leaking problem still there? Because you need to solve root cause of staining. Once it is done you can renovate your ceiling using POP or else, as below image depicts. Just like the new home builders provides the designed ceiling.
As said above, water stains are tough to cover, even with a stain blocker material. But know your chemistry; a water stain is near impossible to cover with something that is soluble in water. So a water or alcohol based stain blocker isn't going to work. It has to be an oil-based product, and even then it may take more than one coat.
I used to use the original KILZ in a spray can but it was shellac based and thus water soluble. It worked, eventually.
Posts: 12178 | Location: Ft Collins, CO USA | Registered: Sep 18, 2002