The trick is to keep the large spools of film in the bag, and in the open canister so it doesnt unwind.
I roll like 40-80 rolls at a time in the bathroom, not fun, but I think of the rewards after.
How not to spool 400 ft of film into canisters!
Years ago I worked as a junior darkroom assistant in the back of a camera store in Brisbane. The proprietor sold Leicas but most of his money came from selling film. He had a scheme of buying Ektachrome in 400 foot rolls and getting darkroom junior (me) to cut 5 foot 3 inch lengths and load empty 35mm cassettes. Everything was done manually in a darkroom with cassette bodies, cores, ends, film tape, scissors, and a bench top with a measuring nail all laid out exactly. Then I made a big mistake.
About 20 minutes before closing time I dropped a naked 400 foot roll and it clock-springed into huge tangled festoon of film loops about a yard across. In pitch blackness I could not find the end to try to re-spool it. The stuff was worth hundreds of dollars , the store was closing, I had to open the darkroom door, I had to leave. I was dead. Or was there a way out?
The garbage bags, of course! Gathering up armfuls of film loops I managed to stuff the whole lot into a huge black plastic garbage bag. That bag went into another bag, into another bag, and so on until the mess was light tight. At closing time the boss opened the darkroom and saw everything in order. He didn't look behind the door.
The next day I got the film tangle out of the bags and just started cutting 36 exposure lengths from any loop I could grab. By lunch time it had all been loaded and labelled. The several short left over ends were easy to hide. I walked out of the darkroom sweating but smooth faced.
That film had been kinked, stepped on, scratched, buckled, and abused. Hundreds of transparencies came out of that unfortunate roll, mainly from Leica users, but there was not one single complaint. Amazing!
The "proper" way to do it is with a pair of rewinds, and split reels to hold the film on the cores while you wind it. I'm all set up for that, and it's pretty easy that way, but if you're only ever looking to do a couple of 400' rolls it's not worth the investment. The ideas here will work ok but it's imperative you keep the 400' roll flat on its side on a stable surface (preferably on some sort of axle rod) so the film doesn't fall off the core and make an unfixable mess.
Well I guess I have to take back my statement that the mess would be unfixable yikes! But if you like your film and want good results from it ...
Dude, I just gave you a way to do it with no hassle, get yourself a bulk loader and make your own spool-core, it's not even hard to do. :P
Fuji (Legacy Pro) 35mm film came with metal spools which I have been saving for such an adventure. When the spools are full I have + or - 100' I also only have 3 or them but I fill them up and what is left over goes on a smaller core and put in a loader.
I do not know from where you'll buy the film, but it must be near film making industry ?
Why don't you ask if you can borrow a darkroom a couple of hours and ask them if you can re-spool the 400 ft into 4 100 ft spools ? They probably have a winding device just for doing that and will be more experienced than you in handling 400 ft of film in one single piece. find boxes and masking tape to put the 100 ft pieces into, have a bulk loader at hand to check what amount of film it can exactly handle, be gentle and friendly and prepared to pay a beer or two. That may do the trick...
Start the spiral by hand and spool it over in the dark on a smooth topped table. You don't need a core. If you get the bigger Alden loader you can get 200ft in there and only have to split the roll once.