Welcome to Apug, Philip!

When I started photography I did bulkloading from my 4th(!) 135-cartridge on, using 100' rolls. I did not even know that something as bulkloaders existed. I had neither a darkroom nor a changing bag. All worked fine. I just spooled the film onto the reel up to its flanges.

Best would be to give a 400' roll some container to hold it whilst re-spooling. A glaced conical pot could hold the roll touching only its flanges, no dust, no scratches, no static electricity.