Remove all furniture from the room to be painted, or place it in the center of the room and cover securely with a tarp or dropcloth.
Mix warm water and dishwashing detergent in a 5-gallon bucket. Wash the walls thoroughly with a sponge mop, scrubbing vigorously to remove all dust, dirt and oil form the wall. Rinse the wall thoroughly with clean water, and allow it to dry for 24 hours.
Spread plastic sheeting over the floor, and secure it at the base of the walls with painter's tape.
Prime any wall not already painted with light-colored latex paint. Apply latex primer to the wall with a roller, using an angled nylon brush to prime corners and edges where the roller cannot reach. Allow the primer to dry overnight.
Apply a base coat of very light blue latex satin paint with a roller. Use an angled nylon brush for corners and edges. Allow the initial base coat to dry for six hours, and then apply a second base coat. Allow the second coat to dry for 24 hours.
Rinse a painter's sea sponge in water and wring out thoroughly. Apply a thin coat of light blue-green latex satin paint to the surface of the sponge with a nylon brush -- dipping the sponge in the paint will over-saturate the sponge and create blotching.
Gently apply the sponge to the wall with random curving motions, overlapping previous strokes. Do not wring the sponge or press it hard against the wall or blotching can result. Step back from your work frequently to judge the density of the secondary paint layer.