My most successful bench-pressing phase involved doing band work between sets. I'd been experimenting with various types of band-only exercises for the back – slow pull-aparts and holds in various positions – with the goal of finding weak or sore spots and spending time contracting against the bands in those spots.
I started to incorporate this band work between sets of bench pressing. There's a small track at the T Nation gym, so after each set of bench I'd perform various band holds while walking the length of the track and back, giving me about a minute under tension. I'd then take 15-20 seconds and set up for my next bench press set. During that time I made very rapid progress on my bench, but more importantly, my shoulders felt their absolute best.
I recently began using this approach with a client who had shoulder issues. He went from doing 225-pound bench presses with shoulder pain to doing 275 pounds for 5 reps without any pain. It certainly works!
There are many ways of doing pull-aparts. When I use them as extra work between sets I don't count reps or time – the goal is simply to put the muscles under tension, not to do a specific number of sets and reps.
Once tension is established, simply do slow movements until you find a sore or weak spot. When you do, spend some time keeping that spot under tension until the pain/soreness decreases.
The second approach is to do isometric holds in various positions. This is great to improve muscle control and transfers well to the bench press where the back muscles must work isometrically to create a strong base to push off from.
The last method is to do regular reps, but slower than usual. This is more for muscle-building than improving weak spots or improving the role of the back in the bench press.
Depending on your objective, you can vary the approach. It's practically impossible to overdo pull-aparts, so use them often.