I'm not saying do it "slowly" or having a delay, I am talking more about having greater time between maximum, not start of, angular velocity of the hips and maximum, not start of, angular velocity of the shoulders.
From "Sequential Body Motion and Shoulder Joint Torque Between Baseball Pitchers of Various Levels, Arnel Aguinaldo, Children's Hospital San Diego:
"Professional pitchers rotate their torsos much later in the pitch cycle (34+/-5%) compared to lower level pitchers."
From "Kinematic and Kinetic Comparison of Baseball Pitching Among Various Levels of Development, Fleisig, Escamilla, etc, Journal of Biomechanics, Volume 32:
Average % pitch to maximum pelvis angular velocity:
Youth - 37%
Professional - 34%
Average % pitch to maximum upper torso angular velocity:
Youth - 49%
Professional - 52%
While the youth exhibits a 12% time difference between hips and shoulders, the professional pitcher exhibits an 18% time difference.