Prepare your work area. Lay down plastic sheeting to cover the floor next to the wall you are decorating. Lay out several plastic containers; paper towels; foam brushes; a wide, shallow container filled with water; and an old toothbrush.
Set up the wall surface. Dust or wipe down the area you plan to decorate on the wall, using a damp paper towel. Use a ruler and pencil to measure and mark the area where you plan to stamp. Mark where you plan to place each stencil on the wall.
Pour a small amount of acrylic paint into a plastic container. Add several drops of acrylic paint extender and mix it with a small sponge brush.
Brush the stamp with one paint color. The paint should thoroughly cover the surface of the stamp, but should not be dripping wet. Stamp the wall where you have marked, applying a light pressure.
Blot with paper towels. Lift the stamp off the wall and press firmly into a stack of damp paper towels. Sponge-brush the stamp again and repeat the process on the wall.
Clean the stamp in between colors. Dip the stamp in a container of water to rinse off any leftover paint. Use an old toothbrush to scrub out paint from the crevices of the stamp. Mix the extender into another paint hue and repeat the stamping process.