Heat the white vinegar in your microwave until hot, then pour it into your spray bottle.Pour the Dawn soap into the bottle as well, then put the lid on and gently shake to mix.Spray liberally around your tub and/or shower. Let the mixture sit for 30 minutes to an hour. When using, make sure your bathroom is as well-ventilated as possible. Turn on the fan and open any windows, because this stuff is POTENT.Scrub (if needed) and rinse well.