Creating a secondary .nib
It’s nuts how hard it is to find an accurate (and more importantly complete) guide to creating a secondary .nib to hold a secondary window and controller in XCode/IB.
I stumbled across the SimpleMultiWindow example in XCode’s Sample Code (/Developer/Examples/InterfaceBuilder/SimpleMultiWindow), and it contains all the pieces, as well as how to send messages and call methods between windows. Handy as a guide to work from.