BT, you get the utmost respect for this opinion and advice. Best Answer status for your honesty and candor.
I've not had that experience with your product...in full anyway. I use it sparingly to lightly coat a specimen. The roll of the cotton swab doesn't lift the gummy residue but lays down the VC. I leave it exposed to allow it to spread evenly across the surface. I agree that the residue gets softer on the surface, but perhaps it takes time this way to work through it to the surface. That said, I've not considered it for use with a coin over maybe $25. This S VDB would have me considering a professional conservation while submitting it for slabbing (it's actually what I would do). As for finding that antique flip with a treasure...I understand your enthusiasm!!
The rest of the story. Two or three of what I called folders were actually Premium Cards/boards. One was for Barber Dimes but can't remember the others. I kept a few coins from the cards and added a few to fill holes. All the coins were pretty much low grade stuff. At some point I put them on Ebay and could not believe what they brought, crazy prices. Sometime later I figured it out. The buyers didn't want the coins. They just wanted the Premium Cards. Never thought they had much value. The images below are close examples of what they looked like. Wish I still had them, just for fun.
Thanks for posting that story - very cool. I too did not realize there was such a strong collector market for those boards. OOOPPPPS! I have thrown a couple of those boards away over the decades. I never saw them as a "real" storage device unless you want your coins to corrode. LOL But...apparently: me = dummy
David Lange of NGC fame has written books about these early coin boards, as well as great articles. https://www.coincollectingboards.com/