Electric cutting shears (pictured) helped. The yellow ones are the old fashioned manual tin snips. I used those, too. After cutting the pinwheel out I whipped out the Dremel tool (looks like an archaic dental drill).
I used a grinding attachment to make patterns on the sheetmetal.
And I used a wrench to make it wavy. I wasn't sure how to tack the bent ends onto the pinwheel. ( I absolutely had to fasten them down somehow, they were very sharp, and the metal was too thin to bend down permanently without creasing the pinwheel.) On the cheap plastic ones, the tacking down is usually accomplished by a bead or button. My clever husband had a great idea: a riveting gun. I expected something that looked like a gun or at least a tool with a cord. Not so. The thing looked very unglamorous, a bit like a three-hole punch. It did the trick, as you can see below.
Next post about this project will be how I stick the leaves onto the rebar stems. Any ideas?