1. Grab a bottle of McNett Mirazyme.
Mix about a half-ounce into a gallon of water and use a nylon-bristled vegetable brush to scrub the gross spots. (If mildew plagues your whole tent, dissolve a full ounce of Mirazyme into a bathtub and scrub down the whole thing.
2. Set the tent up outside in the shade to let it dry.
3. Now mix 1 cup concentrated lemon juice (the type that comes in those little plastic lemons), 1 cup of table salt, and a gallon of hot water. Use a sponge to bathe the whole tent. Then let it dry thoroughly before packing.
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That’s good; I’d never heard of Mirazyme.
I’ve always made major use of Chlorox. Diluted solution totally cleans water bottles, anything (except very careful on the nice clothes). Then I soak in solution of vinegar (cheaper than lemon juice). The vinegar trick really helps on the synthetic clothes, which tend to stink even after being washed.