Keep shoulders back

So my chest was a huge point forever until I tried a few new things. My triceps would always fatigue before my chest got a good workout on flat or incline bench or db. So what I started doing is pre exhausting my pecs with cable flys before doing flat or incline bench. After 5 sets of 8-12 with that my pecs are pretty fried then when I go do the rest of my workout they actually get a workout instead of my triceps. I've seen huge improvements doing this over the last 4 months or so even while on a cutting diet. I can only imagine what's gonna happen when I get back on a bulking diet.

And what else really worked for me is slowing down my reps a lot a worrying more about feeling every part of the rep and totally forgetting about the weight. Slow negative and positive and a hard squeeze at the top but not locking out. I usually don't go below 10 reps on chest. I've made more progress in the last 6 months doing this then I did in 2.5 years prior throwing around heavy weight.

Complete isolation is physically impossible when it comes to bench pressing, and pretty much any full range motion exercise.

Bench press involves the pec and anterior delts to pull the humerus inward towards the center line of the body. Then the triceps to extend (straighten) the arm at the elbow.

You can de-emphasize the triceps by doing flies with your elbows locked. Them de-emphasize the delts to an extent by decreasing the angle of your arms to your body. For instance, increasing the angle would be going from flat to incline bench. This would place more emphasis on the delta and less on the pecs.