I used to feed 12 horses in a pasture situation. Pecking order in place and everybody knew where they had to be to be fed. But that was an established herd.
The Icelandic people have feed stands...a standing stall, horse width, several in a row, closed behind with a rope or chain, feeders in front. Everybody goes in one, usually the same, stand you dump in the feed and then close them in, until everybody is finished. Extra aggressive horses have a solid divider, at least for head and neck, so Mr. Timid has a fair chance, too.
You can put them right at the fence line so you can dump the feed in from the outside, then once they're eating, close them in.
Should you have a high ranking one eating little, slow him down by adding a couple of big rocks, so he has to look for each morsel, or a large pan, so it's more spread out and harder to wolf down.