I made card templates for the front and back by laying a piece of construction card over the frame and drawing around it. I added a little extra for folds for joining purposes, then cut it all out, folding the card as appropriate.
Once done, I folded it all flat again and did the same trick with spraying left-over spray paint around the edges to mark where to cut. Then it was the hard labour with the metal scissors again that kept me busy for a while. So long as you wear protective gloves the sharp metal edges are not a problem.
Folding the metal is a challenge - at 22 gauge it's pretty tough. I clamped it to the work bench and used a scrap of 2x4 lumber and a large hammer to pound it into submission.
For the tight spots I bent the parts that will be hidden using heavy pliers. This was hard work!
The metal comes with a film of machine oil on it to prevent rust, so it smells like an old battleship. I'll have to wash that off with detergent before painting or gluing. Hence the mess on the photos.
The folding is not hugely accurate, but this K9 already has a very authentic sounding 'clang' when struck, and the metal is thick enough that it doesn't dent if you rap it with knuckles.
Something tells me it's going to be heavy though...