Airless spray is becoming more and more popular as a way of applying ready mixed plasters and even powder plasters if the equipment is suitable to handle the product. Different thickness will require different machines.
Skimming only - up to 1mm
This can be pumped through a standard airless spray machine. It will skim plasterboard or similar internal surfaces. The technique is very similar to spraying paint.
Skimming and Levelling up to 3mm
Also can be pumped through similar machine, but once sprayed it would require caulking or smoothing with a spatula or trowel. This thickness would be Ideal for surfaces as Artex finishes that need to be smooth.
Levelling up to 6mm
To spray products with aggregate or a level up to and over 6mm thick you will need to consider a machine such as the Wagner Plascoat. This is much more powerful and able to apply this thick.