The buss bar would energize every circuit. I'd do similar, but remove every neutral from the lug and connect the battery to each neutral and find what is energized. Doing so one could reattach every necessary neutral, and tap off/cut off each not needed. Lable each circuit as you i.d. it as well.
The nice thing about doing it that way is the battery could be attached to an outlet and test back at the box, larger circuits could be i.d.'d that way as well.
Just need to make sure all the neutrals are removed from the lugs, in the main, and any subs.