the diffusion device looks similar to what i have for my lumedyne - i think it is called " the tupperware lid"
ed: i know the person i spoke with ( also ed ) spoke about pre-exposing on frame by frame basis - by double-exposing and shifting where "zones of detail" would be. he used to do it with both color chrome film and b&w film. i know what you mean about re-rolling film. i used to use a yashica-mat double and did a bunch of double-exposed images. no re-wind button, and it *was* a royal pain in the neck to re-roll. nothing ever alligned the way i wanted.
this is great! its good to know this technique is still alive and well, and when i eventually try "pre-flash" work, i can ask for some useful advice from people who do it
(i wish i had known about this before when i had lighting-conditons-from-hell to deal with.)