Question for the plasterers on here ... painting options?

[JRC]

I know what you mean about a smooth plaster finish. Unfortunately, most of my walls lost that pristine smoothness over the years due to being painted, or from when the house was uninhabited, and the plaster was subject to freeze and thaw. (this caused the skim coat to delaminate from the brown coat in spots) But, the plaster in the foyer is still fairly well preserved in its smooth state.

I'm no expert on paints, but it looked to me like the last people to paint the foyer used extremely thin paint, and brushed it on. There was no sign of the orange-peel texture that you get from using a paint roller, and if you looked very closely, you could see brush strokes VERY faintly.