Warm a clothing iron on the "Low" heat setting.
Hold a clean cloth over the crayon marks on your wall. Press the warmed iron onto the cloth to melt the crayon wax and transfer it to the cloth. Keep the iron in place for 4 to 5 seconds at a time. Move the cloth to a clean portion as the crayon wax is lifted.
Spray the remaining crayon stain with silicone spray. Sponge the stain with a clean cloth until the color and wax are removed.
Pour 2 cups of warm water into a bucket. Add 1 teaspoon of dishwashing detergent.
Dip a stain-erasing sponge in the soap solution. Squeeze out excess soap solution. Gently scrub the wall's surface to remove the oil deposited from the silicone spray, along with any remaining crayon stain.
Rinse your wall by wiping it off a damp cloth. Dry the surface with another cloth.