The Squeeze-and-Spread Press
Select a dumbbell load you'd typically use for traditional flat presses and set up in a T-bench position. Do the eccentric (negative) phase of the movement with a slow and accentuated squeeze press and pause in the bottom position (i.e. eccentric isometric).
After pausing for 1-3 seconds in the bottom, allow the dumbbells to gently collapse to your chest and then immediately shift the dumbbells to the sides of your torso so that your arms are supported by the bench (hence the reason for using the T-bench position).
At this stage you'll be in a more traditional neutral-grip chest press position. Drive the weights up in a standard fashion, pause at the top, squeeze the dumbbells back together and then repeat this cycle by moving back into the eccentric squeeze press.
What Makes This So Effective?
It allows you to truly overload the eccentric phase. For example, when performing dumbbell presses in a flat position, I typically use 100-110 pound dumbbells. When performing the dumbbell squeeze press, I typically use 75-85 pound dumbbells.
But with the eccentric accentuated squeeze-and-spread press I can use 100-pound bells throughout the duration of the set by simply adjusting my body position to match the strength of each position to the corresponding eccentric and concentric difficulty levels.
A quick note on the transition phase: While the majority of the eccentric squeeze-and-spread chest press feels quite natural and self-explanatory, the transition from the bottom of the squeeze press into the traditional press (the spread phase) can be a bit tricky at first. Spend a session performing several sets using significantly lighter loads to familiarize yourself with the transition/spread phase.