Move all items out of the room. Give yourself plenty of work space including an area for your paint and plaster supplies. Cover and protect floors by placing down drop cloths. Wrap any remaining items in the room with plastic.
Guard any adjoining surfaces from plaster by sticking painter's adhesive tape to the surface. These areas commonly include baseboards, door trim, window frames and adjoining walls. Rub the tape firmly in place to ensure it sticks and that no plaster leaks under the tape.
Roll on the joint compound to the wall. Use a 3-inch mini-roller, because it is easier to handle and roll on heavy plaster than with a larger roller. Cover the entire area, and on your last roll, roll upward. This technique creates wet plaster peaks pointing up.
Hold your drywall trowel in your hand at a slight angle. Use the edge of the trowel and blend the peaks of the plaster downward. Only move in a downward direction. Clean your trowel with water as needed to prevent plaster from drying on your tool. Continue to texture the entire wall.