Slowly lowering the bar/DBs increases the time under tension and helped me greatly in increasing the amount of weight over time.
Ever heard of Power, ranged Rep, shock workouts?
I believe they suggest loading a bar with slightly more weight then your 10 Rep Max (or so) and do slow descents with the weight (having a spotter or using a Smith machine) as in 4 seconds down 1 up. Made a huge difference in my bench strength