Originally posted by Greg Jennings
Addressing the original question: the way I was taught to do katatedori shihonage, the very _last_ thing uke can do is "just let go". It's well and thoroughly trapped and uke is dealing with his balance being oscillated in two directions.
I've seen shionage done in two ways (yes I know this is a bit of a generalization...). Last year (2001) when the present Doshu held a training camp in Stockholm, Sweden, he did a shionage where uke held onto both of your hands and you didn't hold his at all. My sensei has also done this on me a couple of times. The second way to do it is when you hold onto ukes wrist firmly. This is what I'm used to (Iwama style). As others already said, practice! Read my "signature".