To reduce GCT you need to increase leg stiffness. In my opinion there isn't really a single best way but I do things like fast eccentric lifts, stiffness jumps, and various catching (both the body from a fall and / or a load) exercises.
Mike, I remember us having this discussion a few years back relating it to GCT in the hurdles.
I do similar stuff. This may be overly simplistic, but in addition to the eccentric loading in the weight room, early in the season I tend to have athletes "hold" the landing off of a box with as little knee flexion as possible. From there I progress to allowing the contact and subsequent takeoff to be dynamic/elastic.