I'd be temped to pick up the bucket by the edges more than use the rice, though
That would be difficult.
It's kind of funny, the guys at my gym go through these phases. For a while it was flipping bumper plates up in the air with one hand and catching them with the same hand. Then it was pinching standard plates together and picking them up. Then it was the rolling handle static holds. Everyone has always messed with the CoC grippers. Oh, and picking up short bars vertically is another one.
I'm glad you mentioned opening the hands, E. I haven't thought much about that. It's something that I haven't really trained much.