I had to reapply a patch and used a knife blade to scrape off all the old adhesive, like it was a paint scraper. Worked fine. However, I was recovering and wasn't concerned for scraping into the outer layer a bit.
Goo Gone works but will dissolve a bit of the surface material as well. Another alternative is 3M Adhesive Remover 03618, used sparingly.....
I ended up using "Goo Gone", which worked reasonably well. I assume it will not harm the hypalon.
Tolul or Toulene is available at Home Depots in the Las Vegas area for those that drive there from California - right next to the Acetone.Thanks everybody. I spent most of the afternoon running around trying to find tuolene only to discover it is no longer sold in California. Ironically, I have a can of it at home and could have saved an hour or more of fruitless searching if I'd just gone and gotten it.
I ended up using "Goo Gone", which worked reasonably well. I assume it will not harm the hypalon.