What is the best way of fixing minor blemishes in new plaster before painting interior walls? In particular, should I sort them before or after mist coating?
Background:
I bought a 1930s house in the UK, with brick internal walls coated in old lime plaster and wallpapered, painted, and wallpapered again (sometimes several times!). We wanted to freshen up and get to a good painted finish. After removing the layers of paint and paper, the original lime plaster was sound, but had a poor surface texture and carried a number of obvious scars from previous remodelling and electrical work, not to mention lots of holes where screws or rawlplugs have been removed. Hence we have decided to have the lot re-skimmed with new plaster, to give a smooth paintable surface.
The problem:
I know that normal paint tends not to stick to fresh plaster, and the advice is generally to apply one or two mist coats of watered-down emulsion before painting with a top coat. I want the best possible surface finish, so I am also planning to lightly sand down the plaster to remove any drips and splashes and apply filler to any small bubbles. Some brown blemishes have also appeared in the new plaster as it dried, which are probably due to the remains of screws or nails embedded too deeply in the old wall to be able to extract. I know that these need to be sealed to stop the stain from coming through to my new paint, and plan to do this with something like Zinsser B-I-N.
My question is: does my overall approach sound sensible for getting a smooth, blemish-free painted surface? And if so, should I do the sanding, filling, and sealing before the mist coat of paint, or after? Will the filler and sealant have adhesion issues if I haven't mist painted, or will the thin paint underneath make them less effective, or more likely to flake off over time?
