I've learned my lesson... I left my camera with a wet strap inside my bag. A day after.. it's moisture everywhere.. and every lens. I know now how to avoid it though, but I'm looking for something to protect my gears furthermore. I'm now considering of buying a dry box..
I think the quick answer to that problem is not to leave wet equipment in a bag. The real answer is never to leave equipment in your bag.
If you live in an air-conditioned environment, all you have to to is take the equipment out of the bag and put it on shelves or in a cabinet where it's exposed to the conditioned air during the night. You will keep fungus from growning if you prevent it from having a full 24 hours of 70% relative humidity--you just have to keep breaking that cycle.
When I lived in the Philippines back in the 80s, I didn't have air conditioning. During monsoon, our house was so humid we had mildew on the living room walls. I had a wooden cabinet made--not much different from a small china cabinet--and mounted a low-wattage electric light in it. I stored my equipment on the shelves covered by well-washed non-terry dishtowels to keep off dust.
The heat from the bulb lowered the relative humidity in the cabinet enough to prevent fungus growth. It doesn't need to be airtight, it only has to retard convection air rushing quickly in from outside.
When you're living full-time in such an environment, you don't want to be fooling with dissicants every day. Either make a simple drybox as I did or purchase one.