A comment
Unsubscribe about my experience, maybe someone will be useful. He poured a room of 20 squares, taking into account irregularities, it took 20 bags. Gypsum mixture as a fill is very difficult to work with. Firstly, when adding the required amount of water, it gives a very sticky and non-elastic solution. And you can’t add more water to make it easier to spread; after drying, it crackles. Checked by me in a small area of the kitchen. Also, despite the manufacturer's assurances, it will not lie on a layer less than 2 mm. Because of this, it is a little inconvenient to work with a spatula. By trial and error, I came up with an acceptable way of working.
I put a thin layer and slightly equalize it with a spatula, not really trying. Then we let it dry for 20 minutes and remove all the bumps that remain from the preliminary alignment. I think that perfection will be easier to work as a rule, but in a narrow room I did not succeed.
pros
Quickly dries, easily processed after drying, gives a good durable layer.
Minuses
The solution is heavy to fill, poorly leveled.