Instead of thinking in terms of hip rotation imagine your rotation in the back swing as three barrels sat on top of each other. One your upper body, one your central torso and one your lower body. Draw a chalk line down through them to represent your address position.

During the back swing the top barrel line will rotate clockwise about 90 degrees, the middle line around 60 degrees and the lower one around 45 degrees.

This should be a swing thought when practising, it is not an absolute science.