I’ve been told by a former pro bodybuilder buddy of mine that Dumbbell chest flys are the single most important shaping exercise for chest. It’s probably due to the fact that it isolates the chest from the Delta and triceps.
On a flat bench, from the sitting position with the dumbbells testing on your knees, roll back while hugging the dumbbells to your chest. Press them up. The weights will be significantly less than your dumbbell press, so this will be easy. Touch the dumbbells at the top and bow your elbows out slightly, like you’re hugging a tree. Keeping your arms in this hug position, lower your arms to a full fly. You’ll know you’ve hit bottom when you feel your chest stretching. Going back up, keep hugging that tree until you touch the dumbbells again.