Ive done that in the past, take out the center spool of each reloadable cassette and place a strip of scotch tape in the middle, the stick on to a table edge or something. then open up your spool in the dark and stretch out a length (arms wide out to the sides = 36 exp plus leader for me) and cut and tape, and re-roll.

I have done it with, 100ft, 400ft, and 1000ft reels. its mechanical after awhile, but it sure gets boring in the bathroom. I use a long pair of safe tweezers to re-roll film in quickly by the spool through a cleaned felt light trap. as my current method entails using drugstore discards and reloading them.