As we go through life we find things we like...
I really like high quality Duct (100 mph) tape, Zipties, Paracord, and dearest to my heart..."Ziplock freezer bags"
I put everything in Ziplocks when I go in the field. Heck, I sometimes even put Ziplocks in Ziplocks...lol
Good thinking on the "One magazine per bag" idea. And dissicant packs are a great idea too!
I keep my ammo in ammo cans with dissicant packs...works well.
Here's a tip. If find a round that ya really like, buy it by the case. Put it in the ammo can with the dissicant pack. Tear of a box end with the lot code, and put it in the ammo can as well. Mark the ammo can with a number...1 through xx1 as your "can" collection grows.
Make up a table for each can with the following info. Caliber, make, weight, special features of the round, date bought, etc. Compile these tables as a quick reference list.
Such a list can help ya easily find what you're looking for, instead of opening each can to find out what's in it.
Also, I try to find a ballistically equivilent practice round (weight, recoil, flash signature, etc.) for each of my premium defense loads...then I can practice on the "cheap", and still be ready with the good stuff when and if the time comes...