The type 517 I developed today was taped to an old cartridge cut end with yellow insulation tape.You should get 18 * 36 exposure rolls from a 100 foot roll.
You can buy reloadable cassettes like these:
or you can use cassettes that have been previously loaded commercially and still have a bit of film left sticking out. This is a bit more fiddly because you need to tape two pieces of film together and sometimes the film sticking out isn't long enough. Also the tape you use has to be strong enough that it doesn't snap but thin enough to be wound back into the cassette.
If you have somewhere cool to store the loader, then NOT rolling it all at once gives you the freedom to load non-standard lengths when you have a need to do so.
merefilmphoto.com
I'd love to be able to bulk roll film but I know my efforts would immediately end up in the how to ruin a roll of film thread
I could do with a reverse rondinax where the film turns up already loaded in to a light tight thing so you pull out the leader to attach into the canister and then snap it all shut and then wind out the right amount of film into the canister and it would leave out a bit for the next one. It would also have an indicator on the thing to show how much of your bulk roll you have left.