So here is really the first wall we're looking at fixing. This is all kind of bound up with the ongoing winterization and caulking effort; since the outside of the wall needs tuck pointing, the cracks you see to the right of the little boarded-up window are actually letting air in. Yikes! But much more importantly, there was a 1/8" slat nailed to the right side of that boarded-up window, and behind the slat was a really honking big crack from the wall settling.
Here's the crack in its native condition, and forgive my repeated use of Irwinism, but crikey, he's a big one.
Big enough, in fact, that my first step was just to cut up a bunch of leftover Styrofoam (from the box from the overhead light, actually) and jam them in.
That basically fills the crack, so it's a good start. There's a lot of extra air space between the brick layers in there (I believe they've moved a little), but there's not much we can do about that, beyond urethane foam to fill in some of it.
I'll post more on this endeavor later.