[Closed] Painting walls with existing patchy undercoat question

Having pulled the tiles from a wall we want to paint, I am pondering how best to get a good finish. The function of the room is such that its occupant will frequently be spending upwards of several minutes sitting less than a foot from the walls, and I've also ordered quite a bright light fitting, so the blemishes and irregularities which lend such character to the rest of the house will be less easily ignored.

The problem is that the tile removal took with it much of the underlying paint (which is some kind of shiny pink stuff, presumably bathroom-specific) , leaving much of the lower half showing patches of bare plaster. Although the plaster is good and smooth, I'm not sure about the finish with two different starting surfaces.

My current favourite plan is
1 fillsandwashfillsandwashetc until smooth as possible
2 apply a mist coat to the plaster-y bits
3 apply a good quality undercoat, mainly to the lower half
4 2+ top coats

Will I be able to effectively paint over the gaps in this way? Or will I be left with noticeable layers where the existing undercoat remains?