Works for me.
If you’re riding on the right side of the road, it should be your left hand going behind you. Another way to think of this is that you’re turning your upper body to face up the hill. This is similar to the seat-twisting suggestion I posted earlier, but more flexible.
I was taught the same basic rule when I was learning to do backwards spins. For those, face your upper body to the outside of the circle you’re making. Or otherwise, your outside hand should lead the way (behind you).
I’m using my right (downslope) arm, and I understand this as a weight shift rather than twist induction.
When riding, if the road slopes left, place your left hand and arm behind you facing the middle of the street.
When sloping right do the opposite.
It will work