Pour 1 cup of acrylic scumble glaze into the gallon of your first color choice. This should be a light brown, yellow or other base color. Mix the glaze into the paint with a stirrer.
Apply a thin layer of the paint-glaze mixture to the plaster wall with a 4 3/4-inch nylon paintbrush. Use random vertical brush strokes, covering the wall from floor to ceiling in a 3-foot-wide section.
Brush over the first 3-foot section with a dry 4 3/4-inch brush, making downward strokes. Do this when the paint is starting to dry. Repeat with the next 3-foot section, dry-brushing it as it dries, until the entire wall is painted and dry-brushed. Let this coat dry overnight.
Pour 1 cup of scumble glaze into the darker paint and mix it with the paint stirrer. Apply the darker paint in the same way you did the first color, in 3-foot sections with random, vertical strokes. Make the layer thicker in corners and around ceiling and floor trim.
Use the second dry brush to brush the sections with random horizontal strokes as they dry. Wipe the brush on a clean cloth after each stroke. Repeat with each 3-foot section. Let the paint dry for 24 hours.