Over the years I have developed a supply of Ever-clear it was cheaper than Vodka or Gin. The guys at Hasselblad in LA told me that is was they used for lens cleaner. But I guess Vodka or Gin will do the same job. Remember Ever-clear is 190 proof and dries real clean.
You are welcome and good luck, it is just one of those jobs that's a pain to do. But done correctly the holders will work just like new.
You are correct. That is why you never want to do a tape over. And why you need to clean all the old tape glue out of the end flaps. The book tape will stay flexible for a long time it is designed to bend.