I like the ides of griding down a garage-sale wrench. I even have an old combination wrench (unfortunately 7/8" so the wrong size)
we keep tied to 100 ft of parachute cord to throw over limbs in trees we need to cut down but will need a guide/tension rope. Got that one in the trunk of an old car we bought for a dollar from a relative.
The crowded toolhead of a Dillon 550 just makes it tricky to tighten the less-well-supervised dies even with fingers. On my RCBS Rockchucker, they are easy to get to with fingers, or any kind of wrench, if I needed to, but on that press it isn't much of a big deal anyway, as it would be easy to see and tell if a die started being loose - on a progressive like the Dillon, you could fail to notice until you'd messed up some rounds, and on a 'toolhead' or 'turret' application, I figure I may as well tighten them pretty snug, because it isn't like I'm going to be taking them in and out like on the single-stage press.
Even the little sheet-metal Lyman wrench would be plenty strong, and for $3.99, might be worth not having to grind down a 'real' wrench, but I'll have to wait for Lyman to respond to my "What size is your durn wrench?" question before I get one. Until
then, I guess < sniff, snuffle > I'l just have to get by with the channel-locks...