Agreed. Lets discuss shomenuchi kotegaeshi (or any other one would be fine).
If the person attacks with with right arm, I tend to enter and pivot (as if I'm doing iriminage) - keeping vertical main with my spine. Then I would typically use my right hand palm up laying across their forearm giving them a bit of my body weight. My left hand would be between their shoulder and elbow palm on them. That arm would move be bending as I moved closer to them, and then I'd let my body weight start hitting them using that palm as a natural energy release of that movement (same as the hand on their neck for iriminage) except I'd let it slide down their arm a bit to get into kotegaeshi position. Then I roll that hand so more weight is on their arm nearer my thumb than my pinky as I continue to move into shikaku. When I roll back (move body weight neared my pink than thumb) I cut their center with my intention. I don't pay much attention to what my right hand is doing at that point. It's not cranking anything for darn sure. It just barely touches their finger tips usually. But I'm open to suggestions.
Just out of curiosity if I'm picturing it correctly:
So it sounds to me like you're fading/entering leftward to the "outside" of uke's cut, resting your right arm on top of uke's cut (his right arm) as it cuts down; that palm is facing up so you're resting the backhand side of your forearm on uke's tegatana? You then describe the left hand entering near the bicept area and sliding down uke's tegatana to take hold for the kotegaeshi itself. It sounds like you're then taking that connection/hold (your left hand) and then preparing for the pinkie-led kotegeashi movement by loading up a little with the thumb first?
Maybe initial palm up should be replaced with wrist up, fingers down. Looking for inspiration..
Are you describing the difference between resting the backhand side/outside of the forearm and the inside of the forearm on top of uke's cut?