As for the tarnish reducing paper topic, i'm not sure what exactly that is, but something i've read about and considered is getting thin copper sheets to place with copper/bronze coins, have it act as a magnet for tarnish. If it starts to turn, you apparently scrub it well to re-expose the copper. Some people use copper foil, but it's less resilient to scrubbing,do would often need replaced. The paper you had may have been imbued with copper, but long-since spent, served its purpose for a short time.
Regarding cleaning, don't use ammonia on copper, bronze, or even lower purity silver. Or so I've been told. Acetone will work on organic matter, but not likely to affect verdigris, tarnish.
Very neat potential split flan.
You might consider buying the ebook version of the grading book, if you're comfortable reading digital books.