No need to roll off the throttle going up or down, that's the whole point of DCT. The system will detect exactly when to automatically blip the throttle. Just keep the throttle open as you change up the gears and keep it fully closed when you change down. Impossible to damage anything by any manual input. It's one of the reasons why Porsche supply the 911 turbo ONLY with a DCT box (Called PDK), no manual box available, to stop the driver making a hash of the down changes and over revving (Type 2 over rev).