My front delt would always get more sore day after doing incline barbell than my chest did. Fixed inclined barbell racks are usually too inclined. I feel major things to reduce activating shoulders would be lower the incline. Well below 45.. like 20-30 and don't flare your elbows out to the side when you are pressing, keep them somewhat tucked. On the fixed incline racks, it helps to slouch as much as you can to lower your body's incline. There is usually a pretty big gap from the seat under the small of your back.