You've heard of manipulating paint with sponges and rags. But a plastic bag? "You'd be surprised," says decorative painter Ingrid Leess. "It works great."
To start, put down a latex base coat with a satin sheen (it makes working with the top coat easier). Once it's dry, mix equal parts clear acrylic glaze and latex paint at least two shades lighter or darker than the base coat. Cut in with a brush, then use a roller to apply a generous coat in an area no bigger than 4 by 4 feet so that you'll have time to rag-roll before it dries. Press a crumpled plastic grocery sack into the wet glaze, and tumble the bag back and forth in overlapping angles.
"You want to let some background color through to give it a three-dimensional look," says Leess. Move to the next section, overlapping the edge of the first. Check the effect before an area dries. If it isn't right, reroll and rag it again.