Store it in an aluminum salt/pepper shaker and use it to help the hydrogen peroxide in the toilet and tub.
If stains and soap scum is bad and hydrogen peroxide isn't cutting it, after cleaning with hydrogen peroxide, sprinkle some baking soda in the toilet bowl, let it sit for a few, scrub with toilet brush.
In the shower, after spraying with hydrogen peroxide, sprinkle baking soda, leave for a few, then scrub with a scour pad.