I have made half a dozen plaster patches within my home remodeling, each about 30-40 sq ft. The plaster goes over brick, so not lath. It was a hell of a job but still simpler than framing walls and hanging drywall.
I used the old-fashioned plaster recipe: for the inner two coats (it needed that many coats to be flush with the old plaster bordering it because the old plaster is 3/4" thick) I used 2.5x masonry sand and 1x hydraulic lime (by a company called Virginia Lime Works). For the finish coat I used 1.5x really fine sand (by Quickrete) and 1x the same hydraulic lime.
In preparation for painting, I was told that before applying primer, the presence of lime in the plaster required neutralizing. I am not sure about this so I am asking to confirm. In addition, are there better solutions to neutralizing than vinegar?