I would try to use more dumbells for presses (rather than barbells) and concentrate on the movement slowely going down, making sure you stretch the chest and exhaling when pressing. If you're going to do barbells, make sure you get a slightly wider grip, which may in your case put less emphasis on your shoulders...
Your shoulders taking too much part in your lift usually means one of two things: your shoulders are weak (much weaker than your chest) so you feel them tense up and it feels like they are doing most of the lifting (when I assure you they are not) OR your chest needs a lot of work, so to perform the lift, your shoulders get in there and support your chest and help you lift.
You can also do some machine presses with a bigger range of motion, which may under-involve the shoulders.
Either way, lower weights on chest exercises means less shoulder involvement, so do that as well.