I’m guessing it repairs the diaphragms of the 3 door elements [with their 4 diaphragms each]. A lot of us on this FORUM are pretty good DIYers and I'm now doing much of the repairs on 3 of these vintage MBZs and although not yet, I'm sure I will face the same decision you did when you were motivated to develop your "technique" ! I could probably dream up my own workable repair but sharing ideas I thinks is the best thing about this FORUM for I believe it improves the quality of DIY fixes... e.g. maybe I might have a seemingly small idea that significantly improves upon your "technique".

I think I have better "tweaking" ideas than I do original ideas!

Best regards,
Sam