david weaver
I think hacksawing would also work if you were willing to do a shortened version of what I do down the iron slot. Not sure if the cut temperature at a hacksaw blade edge could create any problems or how long the teeth would last on thin material, but it should be doable slotting just part of the length and drilling the large hole at whatever end it's on.

I haven't tried it yet, but should.

Vixens are great (the type that go on a backer and are intended to be flexible for car work) just screwed onto a wooden stick. You don't want one with a conventional handle to work metal, though. Sometimes, it's nice to be able to go parallel along the length of something.

There's a little learning curve with not allowing a tooth to catch along the edge of something, but for a person with no real metalworking tools, they are a good material remover - faster than a file, but slow enough that you don't blow past marks. maybe three times as fast as draw filing. When they catch, a tooth can go deep into the corner of something and spoil it, but my opinion is that they are well worth learning.