Painting the fireplaces second part

Yes, I have been painting our fireplaces again. The stains on them are just showing!
I already did 3 coats and walls are still stained.
My next step was trying to paint it with bathroom paint. It is more covering than ordinary emulsion and also we already have it.

After just a 1 coat all stains were covered!  Than I let it dry and because bathroom paint has a sheen to it I have put another coat of emulsion on top.
And voila! Stains are gone!

So if you have same problem you can try first ordinary bathroom paint before buying some special stain blockers.