Follow http://lib.store.yahoo.net/lib/yhst-17797617870419/twistjawtongs.pdf and get any size flat, not just the one mentioned and 2 pairs of vise grips, when you come to the twist, use the two pairs of vise grips right next to each other to make the twist, as long as you pay attention to the alignments, it doesn't really matter how bad they look.
You can also use round stock with little modification.
Since you've made a nail, maybe you can make ... a nail header - it's fairly easy to do with a railroad spike or a large grade 8 bolt. (The bolt will probably be plated, but this is easily removed in vinegar overnight.)