Just prime and paint like drywall, I never do anything special to it, is still a lot I want to learn about plaster. But have done a fair amount and prime and paint is all we do.
Cool thing about plaster, years ago when you mixed it and applied it, worked it to the desired finish texture you want.. It had a really light pinkish tint to it. But not a solid colour. kinda streaky and in a random patten, looked pretty nice.
Recently worked on a house that was built in the '70's and never was painted, still looks great.
Today the plaster is white and blah, I was a finish carpenter on a new construction house.
The plasterer's mixed regular folgers coffee grounds into the plaster mix, gave it a brown tint and looked beautiful. They had to do it by trial and error to get the right colour.They could adjust it by adding more or less grounds to it.
But again, another plaster job that will never be painted.