[an0nymous]

Message to myself from three weeks ago (and to anyone else wanting the benefit of my hindsight)
1. The washers: Not actually metal. Really there's just a thin metal cover over a sort of hard plastic/rubber. Don't be fooled just because they look like a solid metal fastener.
2. What worked for me: Scratch awl and a small hammer. Angle the awl at a 45 degree angle to the surface of the washer halfway between the threaded post and the outer edge. Use the hammer to punch through the topmost metal (not difficult; tap, don't sledge). Tap the awl and drive the washer counterclockwise adjusting the handle of the awl to maintain the same relative position of awl to washer. Once you get them unthreaded far enough, it's finger work.

Do not waste hours trying to grab the edge of the washer with the tip of a succession of needlenose pliers and channel locks. This way lies madness.

Thanks, guys. I was just skerred. Once I gave it a solid whack and stopped worrying about the finish on the washer, it was easy-peasey.