I just use these feeders. Three for 24 chickens. I bought ours at
Tractor Supply. I like that I can clean them periodically and it takes little time to fill them. I bought a couple (one and a spare) of
flexible handle bins at Dollar Tree that hold several pounds of feed. They squish, funneling the feed into the tops of the feeders easily.
I originally thought I'd like a hopper-type automatic feeding system, but I've found that I like to spend a bit of time with the chickens in the evening, observing to see how everyone is doing and talking to them while I tend to their food and water needs as they snack on some scratch. I also like that I can place feeders in three different locations, ensuring that those lower on the pecking order always have access to a feeder.
After raking the deep litter into piles in the evening, I also will take an old large serving spoon and scoop some crumble out of the tops of the feeders and put in small piles onto bare places in the run. It gives them something to do in the morning before I get to the run to let them out, or if they're stuck inside because of snow. I make ten or twelve small piles of feed for them to scratch and peck at. I don't find any feed is wasted - they seem to find it all!
Screw hooks in a beam/rafter with chain and an S hook is all that's needed to install. I adjust the height so that it's both comfortable for them to eat and so that they can't kick wood shavings into the feed. I'll probably install alternate hooks in the rafters to move things around every now and then as a boredom buster.
The run door stays open about 10-12 inches during the day. I have not seen critters other than the chickens access the run. We have five cats and a dog, so I think there's enough activity around that critters other than chickens getting their food isn't an issue.
When the door is closed, every opening is covered with hardware cloth, protecting chickens from predators and feed from rodents.