Pre-exhaust your chest by doing flyes first. Then follow with flat bench. You don't need to throw in decline or incline. The pectoralis major is commonly called upper, middle, and lower, but it is ONE muscle group that gets hit in its entirety with flat bench.
Two exercises for the chest will rock your pecs when done correctly. Try this HIT routine (with a spotter):
1. During the concentric (positive) part of the movement, move slowly, deliberately, and with good form. It should take about 3 seconds to perform the entire concentric movement (you prolly normally take close to 1 second to perform this move, so slow down).
2. Hold at the top (without locking out) and the bottom of the movement deliberately for .5 seconds. Never give the muscles relief by resting the weight on your chest (or somewhere else).
3. During the eccentric (negative) part of the movement, move slowly, deliberately, and with good form. It should take about 4 seconds to perform the entire eccentric movement. Because your muscles are 40% stronger during the negative phase, have an experienced spotter add some weight by pressing on the bar (carefully) if you want more NASTY burn!
4. Repeat the pause without resting the weight anywhere (as in #2 above).
5. Do another rep as listed above until you have done 10-12reps. If you can do more than 12 reps, you need to add weight. If you can only do 8 or fewer reps, than you need to lighten the load.
6. Try to acheive MMF (momentary muscle failure) with every set. BTW - Only go to failuire with a spotter or some form of spotting rack, smith machine, etc.
7. NEVER bounce the bar off your chest. This is cheating and doesn't allow the muscle to stay under constant load. Plus, it can lead to bad form and even injury.
8. Before your set, see yourself (in your mind) performing the exercise successfully. During the entire set, concentrate (with all of your will and mind power) on your chest. Envision it growing while you are working it. See it (in your mind's eye) performing the exercise. BTW - this is not bunkum. This works!
A spotter is essential for TRUE fast muscle growth. You have to achieve complete and total muscular failure (teardown) to really push past the envelope. Plus a spotter can assist you during the concentric phase when your body still has strength left for the negative!
Also, for maximum growth potential, you have to work stabilizers, secondaries, and antagonist muscles as well. I.e. triceps, deltoids, lower and middle trapezius, and lats.
If you follow a slow, proper HIT regiment I guarantee quick muscle growth (strength and size).
-Rip