Hi Peter.
I think the way to do this is to make both bends at the same time. A joggling tool is used to form an offset like this for joining sheet metal for car bodywork and the like. It is a pliers like tool with opposing steps in each jaw.
You should be able to set up a couple of pieces of steel in a vice ideally equal in thickness to the required offset. Put one plate on each jaw with the brass sheet in front of one and behind the other. As you tighten the vise the joggle will appear. A bit of trial and error to determine the necessary gap between the pieces of steel may be necessary. More difficult to explain than to do. I can do a sketch if you need it
Jim