To be honest, I enjoy decorating so much and have become very efficient at it, and have saved 1000s by doing it myself. That said, it took me over a year to truly perfect it. But I was not
a developer at that point so it wasn't like I was learning on the job. Plastering I would be learning on the job and I could potentially cause massive delays and problems. But it doesn't seem that dissimilar to decorating, except the prep work before skimming and the finishing off procedure.
Depend on your trowelling skills
It might seem that it is going on to an even thickness, but play with it too much don’t apply enough pressure, you’ll end up with ripples in the finish, and they look horrible, especially around lighting