I have a Zojirushi Tuff Slim thermos flask I've used on and off for years. It has the usual tea residue on the inner lid's plastic, in some areas quite stubborn, and some stains on the inside of the flask. There is a video available on how to clean Tuff products, but I would appreciate your recommendations. Implements I have available include: bottlebrush, Mrs. Meyer's dish soap, Dawn dish soap, Bon Ami powder. I would be willing to get denture tablets if you have had those work. I would like to give it a really thorough cleaning.