ditch all the barbell stuff first. If your genetically powerful in the shoulders chances are you have a high chest, so you want to isolate the chest better by making decline work a staple in your chest routine. I like some of the hammetr strength machines for my chest as well, I can adjust the seat height so I'm forced to push more from the lower chest/abdomen rather than shoulders. On your incline db presses, use a lower incline such as a 20-30 degree incline rather than a 45-60 deg. pushups work well too as a superset b/ db presses or hammer strength machines. I have the same problem you do, and all I've been doing is utilizing these tactics lately and my chest has exploded into new growth. Oh yeah, flys too. Guys like us build really well with flyes and dips as well. I steer away from the pec deck and do more db flys. Again, the pec deck its easy to incorporate shoulders. Good luck and happy growing!!