This formula will work just fine. In a 16 ounce spray bottle, add about 4 ounces of clorox to the water. Spray the stain and watch it evaporate. You may need more than one application if the mildew is excessive. A 50/50 solution also works on water stains. If you then wash your walls the Kilz will not be necessary since this is used mainly as a stain blocker.