Thanks for the vacuum-cleaner idea, WIChix, but I ended up opening up the motor before I saw your suggestion. I tried to fiddle around in there without hurting anything, and then when I was trying to put the motor back together (without having removed the brush) I realized it opened up into more parts than I had tried, if that makes sense. I had it in two parts, and there is a third part that popped off when I was trying to put it back together. I tried to poke the brush out with much better access -- and there was nothing there. It had fallen into the motor while I was trying to put it back together. I managed to reassemble the motor, no idea if it worked before I did that or if it'll work afterward, but at least the $^##&* brush is out.
Incidentally, I never want to open up a FW motor again. It was hard to open, hard to work on without fearing for its life, and really hard to put back together.
Now, to get that second feed-dog screw out...
Ila