Another problem solved...
I was ballasting the last remaining mainline track and got a little over-zealous ballasting around a switch and again got stones into the manual mechanism. So I removed the switch machine and turned it upside down to successfully shake out the stones. When I went to re-install the machine, the ballast had invaded the space where it sat and kept it from seating properly. So I got the shop vac and removed all the loose stones. When I went to re-install the machine again, I noticed that the little spring wire that connects the machine to the moving point arm was missing.
Uh oh! I vacuumed it up! I now had to find it in a proverbial haystack of yuck. What to do? The spring wire would be invisible in the vacuum's tank. It's spring steel, therefore it's magnetic.
I've been collecting the old Soni-care brush heads because they have very strong rare-earth magnets on them. I took one of them, swished it around through the muck and Voila! Out of the muck was the spring wire. Problem solved!
Interestingly, the roofing gravel that was vacuumed up was also sticking to the magnet. Something in it is mildly magnetic. This may be something to consider if folks that run post-war Lionel trains with magna-traction want to use this inexpensive material to ballast their pikes. It may be attracted to the axles and therefore the gear train.