First annealing the brass. I heat it up as hot as I can get it and let it cool down again. It doesn't get redhot (need a larger torch) but every little bit helps to make the brass a bit softer.
Then I bring it back into the shop (don't look at the mess...). I have an extra, very thin steel plate of only 0.3mm thick. This I insert in the previously folded back. I use the anvil from my metal working vise, which happens to be quite large. The hammer is 1 kg.
And then the bashing begins. I try to hit the brass as square as possible to limit the amount of dents. First one side, then the other. I check how straight everything is going to be. Putting the concave side down and hitting from above, helps to correct bows.
This video is heavy metal! So, turn up the volume to amuse the neighbours. Mine were very pleased too.