I am not sure whether I will be doing this in the near term, I am just wondering what the modern (but still analogue) options are and how close they are to the historical processes.
Greg I was guessing one could just use a filter or a piece of c41-processed but unexposed print film to get the mask if necessary; maybe I am wrong. Thanks for raising the issue for discussion....
Thanks everyone for the continued flow of ideas and experience(s). I appreciate it!