This shouldn't be too difficult, I would turn you cowl former out of something hard, steel ideally but brass would probably do. Make sure the front curved section is well polished. Now wrap your annealed sheet around it, then turn the edge over the curved section using a burnishing tool. This can be as simple as the curved back of a teaspoon. You are looking to turn the edge over a little at a time. So you work your way around the circumference with the tool pressing firmly along the circumference, not directly in towards the centre, and gradually turning it over as you go. With practice you will be able to accomplish quite a sharp curve without creases. If it starts to harden and become more difficult to work, then anneal it again. Once you have it all the way any creases can be rubbed out using the tool, you will need to press pretty hard. If necessary finish up with a small hammer. the technique is similar to what you were trying to achieve by spinning, but the material is far too thin for that. Finally use some fine wet and dry wrapped round something flat, a cutting tool shank is good. Rub it down completely smooth, trim to size and polish. This is very similar to the method I use for reshaping damaged bezels and case backs on pocket watches. I would think you might have to try a couple before you get the feel for it, but once you do it's quite straightforward.