idea is as you cant get a grip on the feed neck you drill a small hole through both sides of the feed neck opposite each other.
then shove a rod or similar through and you can use this to unscrew the feed neck. you can apply force to the rod without it slipping or marking the feedneck. depending where you drill it (some odd feednecks have holes round the base) .
bit like shoving a screw driver through a oil filter to get it off.
its a old mechanics trick...