Clear the room of all furnishings or move furniture as close to the center of the room as possible. Take off all outlet covers with a screwdriver and place in a plastic bag or other safe spot. Stick 2 inch painter's tape to all adjoining surfaces to avoid adding texture to unwanted areas. Cover flooring with plastic tarps or drop cloths. Additional plastic sheets may cover furniture in the room for added protection.
Open a bucket of joint compound. Add a small amount of water to the plaster if it is dry and crumbly. Mix well with a plaster mixing tool attached to a drill. Clean the attachment immediately after use in a bucket of water.
Dip a mini roller into the drywall plaster. Roll the plaster onto the wall in vertical strokes. Continue to add more plaster to the wall as you roll in up-and-down sections. After a large area is covered, approximately 4 feet in diameter, swipe the rolled on texture downward with a drywall trowel. Hold the trowel with one edge lightly touching the rolled on plaster. Smoothing will get rid of any peaks created when rolling on the plaster and create small dips and crevices. Continue the technique until the entire surface is covered.
Allow the plaster to dry about 24 hours. Pour latex paint into a 5-gallon bucket and add a paint grid. Roll on the latex paint over the stone-like texture with a thick nap roller. Do not apply heavy pressure. More than one coat of paint is most likely needed, as the first layer of paint will be absorbed by the plaster. Allow the paint to dry between two and four hours between layers.
Peel off the painter's tape slowly. If the tape starts to pull up the plaster, cut away the tape with a razor blade. Move all furniture back into proper position and replace outlet covers.