Glue packing peanuts to the canvas, panel, wood or other painting surface you wish to use and cover with a plaster cloth. Arrange them into your desired shape and let them dry. You can also prepare an armature and glue it to your painting if you choose. It's not mandatory to use an armature if your papier-mache piece is small and/or lays flat.
Mix three cups of water with 2 1/2 cups of flour to make your papier-mache paste. Tear pieces of newspaper into strips of varying lengths. Dip the strips into the paste and hold over the mixing bowl. Use your fingers to pinch and slide from the top of the strips to the bottoms. Allow excess paste to fall back into the bowl.
Apply the paste-covered strips to the armature or over the cloth-covered packing peanuts. Do your best to flatten the strips as much as possible. Continue adding layers until the papier-mache piece is to your liking. Wait to dry.
Paint the papier-mache piece using acrylic, latex or spray paint. Now you may want to paint or repaint your canvas, panel, wood or whatever surface you're using.