When I bench press on a flat bench, while pinching my shoulder blades together, I grab the bar at shoulder width, with my head beyond the bar, then I lift it off and center it over my chest. Then I lower the bar so the bar moves at an angle toward the bottom of my rib cage with the bar resting on my nipples at the bottom of the press. Then I press upward and the bar moves at an angle toward my head, ending up above my upper chest when my arms are fully extended. For heavier lifting, I tuck my elbows in tight to my chest at the bottom.
This gives me a nice chest workout and I feel it right in the center of my chest (pectoral) muscles.
Dips give me a tight feeling across the bottom of my chest muscles.
Incline presses (these day only with dumbbells) give me a good shoulder and upper chest workout.
If you are having trouble retracting your scapula try retracting them with medium to light weights on cable rows, especially seated cable rows with a narrow handle, and lat pulldowns, facepulls, etc.: i.e. most exercises involving pressing or rowing you should retract your scapula. It will get easier over time with practice and as your muscles strengthen. And as it gets easier, you will be able to increase the weights.