i don't know the way to exactly measure 100 feet, but if you know your height .. it is equal to your ARMSPAN
and you can just pull armspans of film out, and respool them onto a core ...
you might invest in 3 additional bulk loaders ( i have a lloyds and it is as cheap as they get ) that way you can
just divide it into your 4 holders and not worry about it.

maybe ask friends far and wide who bulk load if they have any cores to make your life easier ..