The plaster-like material that is used for drywall is called joint compound. It is sometimes called plaster because the process of applying it is similar to the process of applying plaster. There are several different finishing levels for drywall. The depth you should be looking for to apply Plaster to your surface is around 2mm thick.This should also, once applied, be as reasonably even as possible, but please do not make too much fuss of your applied Plaster at this time because once the whole wall/ceiling is Plastered onto you can start to trowel out some of the ridges later on, thus said, you should not be putting clumps of Plaster onto your surface, & where you have just applied your strokes of Plaster, don’t play with it too much once it is on the wall, instead, lay on a band of Plaster, & smooth out your strokes so that you have a reasonably level Plaster application the first time, then move onto the next section of your surface to be Plastered until completion.Mix powdered joint compound in clean containers using clean water. Use a mixer similar to a potato masher. For large jobs, consider using a mixer attached to an electric drill. The water should be at room temperature. Reblend the water that may have floated to the top of premixed compound by mixing thoroughly. Do not add more water to premixed compound.Use only clean tools. Dirt, grease and rust will contaminate the joint compound, leaving visible stains and inhibiting its drying time. Clumps of semi-hard joint compound that are not removed from tools will leave grooves in the finish and require more work to make the finish acceptable.