I would play with different exercises until you find something that works. I would suggest incline pressing/incline cable flyes.
Whenever I am working on a lagging body part, I will use moderate volume at a high frequency. So, If you hit chest on national chest day (monday), you would include some incline work with your regular protocol. Say your next chest day is friday or saturday, then I would hit just incline on wed or thurs. I'm not talking about much volume, but more of what Thibs' would call an activation workout.
I've found this works best with your normal weights, but very few reps. You should finish feeling energized, and come back stronger on your next full session.