I have an old 5-quart pro model (model number KSM5PSWW). I had to disassemble the machine and was having trouble figuring out how I'd remove the armature when I realized that I could bend a paperclip and use that to push a broken brush out of its hole. I got it out far enough out to grab gently with a pair of needle-nose pliers. It was a bit of trial-and-error to figure out the correct rotation of the brush, but I got there.
The machine is working properly now.