Yes. That is correct!
PacNorth is correct that Ohmeters can not be used on a hot circuit. However your charge circuit seems rather disconnected! But yes, your best with the battery disconnected.

If you later want to check for voltage drop, that gets done on a hot circuit. The 1948 and '53 Master Tech booklets explain how to do volatge drop tests.

And as far as a mess, I dunno about that. Slow down if you need. Take notes, even if you toss 'em later, for most of us they help with this complicated stuff. For wiring, my notes are usually drawings. The messy versions I don't post, even when I keep 'em.