What you're calling the cement coat is usually called the brown coat, and then finishing plaster.
I have repaired plaster very often.
Here is a quick rundown of procedure
remove and dust out loose material from holes. if large enough and lath is removed- cut back to halfway into studs and cut a piece of sheetrock that is flush or slightly less than flush.
use 1 1/4 sheetrock screws and attach rock and with a touch of not over spinning them -also screw to reattach plaster around hole to lathe.
do the screws on either side of major cracks also
screen tape over cracks and around sheetrock.
Set tape and any major fills with powdered hot mud.
second coat with same. use a 12' blade and fan out
if there is enough of them on a wall, I will take the second step over the whole wall.
finish skim all with a sandable topping.
sand. prime, look over and spot whatever is needed, reprime those and finish paint.
It has a lot to learn, but becomes a routine once you have it down.