The feeling of doing a tenouchi is similar to squeezing the water out of a wet towel (holding the towel like a shinai). The hand grips should be relatively relax at most of the time (except for tenouchi when executing cuts), and remember to maintain the 2 Vs of the hands in a straight line. When swinging the shinai up, use your left hand to push it up (don't pull the shinai up with you right hand). When swinging the shinai down, twist the hands inward to stop the shinai on the target (tenouchi).