We are building our home and have just finished plastering. How many coats of primer and top coat are required for raw plaster?
One even heavy coat of wallboard primer is needed to seal up the pores and neutralize the ph. If the primer is sprayed I recommend backrolling with a lamb's wool roller to help distribute the primer evenly and push it into the pores.
For the finish paint, 2 coats is a good idea. The same application method can be used.