This time of year I have to use heated dog bowls to feed ff. in summer I have the heavy plastic goat troughs from TSC. works great. The troughs keep the chickens from getting into the ff and scratching it out all over.If you paint it, they will simply eat the paint off it. If you seal it, what ever you use may react with the feed or leach into the feed. Natural wood is non toxic, and would be a much better choice. I'd simply use some cheap screws, and screw it together. When it rots, if it ever does, replace it. If you let them peck it dry once/day, it will be just fine. It will be fine even if they don't peck it dry, I'm betting. I simply go to the dollar store, and buy 3 or 4 cheap dog bowls. Plop the feed into them, and spread them around in the run, or set a couple in the coop, one on their feeding station, and an other one on a hay bale. I simply have not bothered to make a trough yet, though may need to in the spring.