What's the best way to keep a mildew free shower/bath? How do you treat the existing mildew?Bleach, bleach, and more bleach.
Sadly, my shower is far from mildew free because I'm lazy and the biggest problem is getting yourself to a clean starting place with no mildew at all.
If you can get there, you can either buy a commercial after-shower spray or mix one up from ingredients around the house. A vinegar and water mixture (as the French would say, a douche for your douche) sprayed on when you get out of the shower will do a good job of keeping the mildew from forming. A few drops of lavender oil in the bottle will help cut the vinegar's strong odor. You can also add some water softener or JetDry to help improve sheeting by acting as a surfactant.
But first you've got to get the shower or bath to a clean starting place, and there's nothing that works better for that than bleach. A bleach-based scrub will be your best bet. It's thick enough to stay in contact with the mildew and the extra friction from the grit in the scrub will help scrape the layers of nastiness off.
And once you're clean, don't slack. Be sure to spray whatever solution you settle on after *every* time you get water in the shower or bath.