This is a common problem once your buildings have reached a certain stage.
This is what I do to not max out my iron bank :
Convert 1 mine to HL
Did not push any mine to advanced 10 (I need the ham more) I stopped at Ad 5.
Farm like rabid rabbit. To get CM to make high end weapons that only need iron. Like timestops. Tornadoes.
Park iron in HA to generate 2/3* feeder troops. (And farm like rabid rabbit for recruits)
Don’t think much before lobbing tornadoes and timestops during challenge events legendary. Not to place high. To complete comfortably and collect completion rewards sooner. Don’t think I can do this for Gargoyles though.
Though not impossible but I think it’s highly unlikely SGG would allow conversion of something free and useless (iron) into something of value that they are already actively selling (food packs)
I use mine (no pun intended) to craft tornadoes, banners and dragon attacks. It would be nice if there was a 3rd queue in HA so that I could use the iron to create troop feeders.
Im in the same situation, too much iron but running out of nuggets for tornadoes and d.bone for timestops. I dont use dragon banners or attacks anymore, they are at 200+ right now. Wish we could bundle up the excess iron into bundles… my HA wasnt working either, running out of tall boots.
Make battle items…. Compete in challenge and alliance events…. Blow 200 or soo axes and bomb attacks each time to try to place higher…. Iron gone… or lb your 5*s