I've made a few flanges; it didn't strike me as very difficult really. 0.2mm brass sheet (that's about 0.008") seems about right, and it can be cut with sturdy scissors and bent in the fingers. A pair of pliers and ideally a mechanic's vice will help a lot though. I bent mine around the shank of a suitable drill bit with a piece of scrap in between to leave a nib-sized gap. A press tool or even a wooden jig would be overdoing it unless you're going into production I reckon, because the final adjustment is easily done with the fingers or round nosed pliers.
A jig would be worthwhile for cutting the slot though, if you propose using a Dremel with a cut-off disc - I guess that would be the professional's tool of choice. A razor saw from the model shop works okay though, but the slot will be
very tight ... a Japanese dozuki could well be the ideal handsaw. Since you propose a bandsaw, does that mean you're going to cut all the way through and fix the flange with a pin, epoxy or both? Whichever way I'd prefer to do it by hand, mostly because I've had enough wood machining, noise and mess to last a lifetime, but it's also easy to cut at a slight angle if you want to give the nib a slight upward rake without bending the brassware.
Hope that helps.
