What are the steps involved in applying a plaster skim coat to achieve a smooth and flawless finish on walls or ceilings?

To apply a plaster skim coat for a smooth finish on walls or ceilings, first, prepare the surface by cleaning and priming it. Then, mix the plaster according to instructions and apply it evenly using a trowel. Smooth out any imperfections and let it dry completely. Sand the surface lightly, apply a second coat if needed, and finish with a final sanding for a flawless result.