Just to echo what others have said, we've done about 6-8 rooms in our house over the past 2 years, for insulation reasons like you. We watered down the cheapest emulsion we could get so that it was about the consistency of full fat milk.
If you've had skim over plasterboard, it can be dry in 3 days, if you've had a thick coat of "browning" onto brick with a skim over, it takes about a week. The way to tell is it gets lighter as it dries. Once the colour stops changing, you're ready to paint
.
I would also use the same watered down emulsion if wallpapering, otherwise the walls can such the moisture out of the paste too quick and cause the paper to bubble/shrink.
Oh and as a heads up, I'd expect some minor (1-2mm) shrinkage cracks in the corners of rooms. So if you have the scrag-end of a pot of emulsion left, don't bin it