Pour half an ounce of paint into the empty plastic bottle. Add one-quarter ounce of water to the paint and twist the lid onto the bottle. Shake the bottle to mix the ingredients.
Lay out your drop cloth. Lay the plywood onto the drop cloth. Maneuver the plywood so that one of the long sides of the board is parallel to the wall, with 18 inches of separation between the wood and the wall. Lift the side of the plywood that is farthest from the wall. Stand the plywood up and lean it against the wall.
Assemble your airbrush according to the manufacturer's instructions. Shake the bottle of water and paint to mix well. Fill the reservoir cup of your airbrush three-quarters full with the thinned paint from your mix bottle.
Set your mixture bottle aside, keeping it close by to refill your airbrush as needed. Refill your airbrush when the reservoir is one-quarter full.
Outline your pattern by placing strips of painter's tape onto the plywood. Trim the tape with your razor knife to achieve the desired shape. Practice painting on the plywood with your airbrush. Use long, smooth strokes following the long axis of your pattern. Press the trigger 3 inches before your pattern begins to ensure proper paint coverage. Remove the tape from your pattern while the paint is still wet. Allow the paint to dry for two hours before shading or continuing with a new color.