A couple of years ago I had to repair a brass headlight rim for my WD/C. I had found the rim in Beaulieu, very cheap, but it had been in a crash or something, it was badly damaged. Well, I've only used a purpose made small dolly and a light bodywork hammer to take all the dents out. No annealing needed, and I was very pleased with the result.
It might be worth annealing the lamp body before commencing work to soften the brass and to lessen the chances of it splitting...There's info on the internet.....Ian