In a large bowl, add 1 part flour to 1 part water. Add salt to prevent mold. Whisk until smooth.
Inflate a balloon. Tape down knot with masking tape. Rest balloon on empty jar.
Dip strip of newspaper into mixture. Squeeze excess with fingers to minimize dripping. Lay several strips over balloon, and smooth with fingers. Repeat until balloon is covered twice. Let dry completely, then pop balloon with pin.
Cut the face pieces to fit onto the balloon. Apply to balloon and brush with Mod Podge.
Cut out trap door with utility knife. Fill pinata with various treats, such as candy or art supplies.