From my experience, (half way through), I'd say you could use the question bank exclusively for the following:
Both comms papers
Airlaw
HPL
Make sure you understand the principles of Instruments, M&B, Flight Planning and Met, then use the question bank.
Make sure you REALLY understand the principles of Gen Nav, then use question bank.
Having not yet gone for the mod 2 brush up, my own personal jury is still out on mod 2 subjects such as POF, Performance, Radio Nav, AGK and OPs. I've heard that most of these can be done just on the QB alone, but I'm not really in a position to comment - yet -