You could just beak down your 400' rolls. Whatever's most usefull. 2x200'... or spool off 100' to leave 300'. Normally you do this in a darkroom, but people often improvise. You need a set of rewinds and one or two split spools depending on what you are doing. I have at a pinch just held a 400' roll in my fingers as I spooled it onto a rewind. Not the safest way to do it.
If you are spooling off your own rolls, you have to spool it twice. The second time you will get the wind orientation back to what it was, and the head, tail relationship correct, so that edge numbers, bar code or whatever they do nowdays will be in the right direction.