Either a simple mixer can be used or a mixer projection pump combination system depending on the nature of the project (specific surface coating, size of application team, projection distance).
Please discuss demands of the project with the equipment manufacturer beforehand and test before large scale use.
Tips
Ensure access to proper voltage (mono or tri-phase, 220V) and electrical power is at least 16 amps if an electrical powered system is used. Water pressure should be a minimum 2 bars and flow should exceed 5 gallons per minute.
Effectively protect areas not to be coated, especially windows, as the adhesion of the plaster to glass is excellent.
Set aside an onsite location for regular cleaning of the machine after use.