Sprinkle the baking soda into a bowl. Pour in the warm water and then stir the mixture to form paste.
Dampen a clean cloth with water. Dip the cloth in the paste.
Rub the hairspray-stained walls and countertop gently with the paste using a circular motion.
Moisten another cloth with water. Wipe the paste off the walls and countertop, thoroughly rinsing the hard surfaces.
Dry the bathroom walls and countertop with a towel.
Inspect the bathroom mirror for hairspray residue. If sticky spots mar the mirror, dampen another cloth with rubbing alcohol.
Rub the hairspray-stained mirror with the rubbing alcohol using a circular motion. Remove all hairspray from the mirror.
Buff the mirror with paper towels. Remove all rubbing alcohol from the mirror.