Since you have the flock party feeder, try that, but elevate it. My rooster can eat out of the flock party feeder o.k. Mine also got a bit of frostbite on his wattles this year, so he didn't eat as well as he normally does for a couple of weeks but now he seems to be chowing down.
I use pellets which may be a little easier to pick up out of the feeder, not sure. I used to use crumbles, but the feed I use doesn't offer that anymore.
I put the flock party feeder inside of a shallow metal feed dish, fits very well, this way if there's any billing/scooping, the feed dish catches the majority of any feed "spilled". I also like keeping the feeders up off the floor, so use platforms. Anything can be used to elevate, a block, piece of wood, etc. A few years back I bought some "chicken feed stands" off amazon, they were cheaper then, but looks like they still have them at around $8-9 each which isn't too awfully bad. The metal stands that I use will hold the water bowls and in summer holds a large 3gallon water station with no problem.
If you give him wet mash, he probably will love that! When I give mash, I still put a dish inside of the metal feed pan, put it on the stand(s) so the feed stays cleaner and it's not flung everywhere.
Nighttime, I pick up the pans along with the feeders and put them in a metal trash can.
Another thought, you can also just put a dish inside of larger dish and provide crumble free choice, it's open and he can have a deeper amount of crumble to "scoop". I have a pigeon that likes to fling her seeds about. I found a silicone slow feeder insert bowl like thing and I put that inside one of those metal pans, it keeps most of her seeds "together" LOL
Stand options...that rooster is about 8.5lbs or so, he has no issue eating from the feeders.
