I know this have been done many times, but there has never been a conclusion. I guess what really matters is type of base (vinyl, acrylic etc) and pigment count. People say farell and ball have high pigment count. Emulsion could be thick with low pigment count (i.e. just jellied up) so runny does not necessarily mean bad.
I sealed fresh plaster with B+Q plaster sealant. It certainly worked, as areas sealed the day before soaked in nothing when I splashed the next day. I painted this with "B+Q colours". Took 3 coats and still not totally "opaque". The colour looked good when it went on wet, but the colour seemed to "soak in" somehow, although the plaster had been sealed. Explain that.
What's this dulux "once". Says on the tin "one coat guaranteed". Money back if not ?
What emulsion should I use to do the conservatory in 1 or max 2 coats ?
Simon.