[header] How to mix plaster [title] Prepare the wall for plastering. [step] Before you get started, make sure the wall you're finishing has already been, and any seams have been touched up with a base coat. That way, all you'll have to worry about is spreading the plaster, which will require your full attention. 
[substeps] Plaster is best applied to wood or metal lath, or bare walls stripped of paint and wallpaper. If the wall has semi-gloss or gloss paint on it, you should prime it before adding plaster.