Something tells me that if you're assisting Michael and Paula this summer, he's going to have you using his system (even for your own work) of keeping the sheets in order with notes to keep them organized and developing by inspection, which doesn't require lots of film boxes, though I think he's mentioned that he does sometimes segregate sheets roughly, for instance, if he knows that there is a batch of shots that will definitely require extended development. And as long as you have such an opportunity to learn to develop by inspection with someone who knows how, you might as well take advantage of it.

Now in general if you don't have lots of boxes or just don't want to deal with lots of film boxes when traveling, and you are using the Zone System or something like it, what I do is to use tabbed dividers that I can organize in the dark, and I can keep -2, -1, N, +1, and +2 in the same box. The dividers are just the cardboard inserts packaged with film and the top divider gets a tab on the top and one in the upper right hand corner along the righthand side, so I know which way the stack should be oriented, and then the subsequent dividers get a sequence of tabs down the righthand side. If I'm shooting a lot of film over a more extended period, I can split the stack into multiple boxes as I load film into holders and generate newly emptied boxes.