Unfortunately, that is about the only part of multiboxing that sucketh.

You have to collect x on one toon, then collect x on the next toon. There's a very small number of quests where all members can loot the same mob (heads, etc) but for the most part it's each kill is 1 drop.

It is a little easier if you go to the FTL (focusless, targetless, leaderless) setup. Once you get all your quest items, switch over to the other toon and have her be the leader.

FTL Setup