But you still didn't explain what you do about cutting the film to length, which is so much better than a strip of wood or aluminium.
When I have a roll of cut film of any width -- it might be 5 feet or 25 feet -- I simply pull out how much I need. How long that is depends on it it's 16mm, 17.5mm, 9.2mm, etc. It also depends on the camera and how many exposures I want to have on that roll. For example, if I'm loading a Minox cassette, with a pair of scissors I cut depending on the # of exposures I want the strip this long:
15 -- 13"
30 -- 20"
36 -- 23"
50 -- 30"