we have exactly the same problem and i can really relate. my knuckle problem is really a pain since i usually don't wear my rings at night so taking it off/wearing it is always an ordeal for me. post # 15 are good alternatives , so i heard from a diamond forum.
2 days ago, went to a local jeweler for resizing and i can basically see his facial "pain look" when i tried to take off my rings. He then advised me to use WINDEX as lubricant as opposed to using soap or lotion... strangely enough IT WORKS!! the rationale behind is that you are making your diamonds sparkly while wearing it. Soap and lotion can stay between the tiny spaces thus can make the stone look lifeless.