We use metal garbage cans, up on bricks, with the feed still in the bags from the manufacturer. There's an empty feed bag on the bottom of each can, again, so the feed stays dry. Our coop is big enough to have the cans inside, so they aren't rained on, and stay dry. Also, a feed bag is cut to be over each lid, and replaced when it gets nasty, with the chickens sometimes sitting on top of the can.
We want to use feed within two months of it's mill date, so we don't buy more than tree bags of feed at a time for our flock.
Mary