I figured part of my problem was working small, so I upped the scale a bit. These guys are the size of my hand, instead of the size of my OK sign. Not sure if it helped. Certainly helped with the hand cramping, though.
I've also taken to writing my notes directly on the drawing instead of trying to add them in with Photoshop. That way they're right there where I can see them without having to dig out the file. Plus it's easier to write. If it's better that I write the notes on the file, too, (to make sure I'm not bullshitting, I guess?) then I can do that.