we do a form of seated tekubi shindo (didnt know that was its name, so thanks
)
my sensei lets the hands shake low and then high (a little above head level), then low, then hi.
recently, he told us to use the vibration to feel for an integration between our backside and our front.
every once and a while i do a seated furitama (didnt know that name either!)
--something i picked up in my early days before i came to my current dojo.
i remember that the creation of vibration was described as a good way to calm ones nerves (center), e.g., an antidote to 'butterflies in the stomach."
also, i like to incorporate sound in the breathing-out--i find it helps encourage the vibrations and makes it much more 'feel-able'.