I don't know if they have a different name in the brush industry, but in fly tying they're called hair stackers.
Yes. They resemble little cannons and have the bottom set to shape the knot without having to clip hair / fiber tips.
Another interesting factoid: "Our original 'glue' was a pearl barley 'syrup'. We used that for most brushes right up to the end of our ownership [of Simpson's]." -Gary Young
I do not. Those quotes are from a different forum. However, you can see cannons in use on several YouTube videos showing brushes bring made. The videos are posted earlier in this thread.