I’ve just sealed some plaster using some of the B&Q sealer (instead of watering down emulsion like I usually do). Three things I like about it…
If the emulsion is non-drip it’s a pain in the ass to dilute, you don’t have to do this with sealer
It’s easier to wash out of brushes
It’s colourless, so if you overpaint or splash, you can’t see it.
I can’t remember what it cost, was not expensive, and personally I thought it was a bit easier.