I was just wondering if the military press will put added mass on my shoulders.
Of course it will!!! depends how much weight you use though. If you lift like a bird than no it wont but lift heavy and yes it will. Same as max said if you have RC problems its not the one but it can be minimised done on smith machines and in racks properly.
All the stuff behind the neck or in front of the neck really makes not much difference except you increase chances of RC blow-out behind the neck as it places more stress to those areas.
Best exercises I have found for shoulders
Arnold presses with d/bells {Whole deltoid is worked}
Upright rows (Arguably the best for shoulders) done so that the bar does not come higher then the nipples {All rounder}
Shoulder press on Smith machine or squat rack {All rounder but good for power}
Lateral raises {Side ''Lateral'' head}
Bent over lateral raises or laydown (On bench) lateral raises {Rear deltoid}
You have frontal raises but honestly you dont need them if you incl upright rows or shoulder presses. The front deltoid gets loads of work with bench press and its hardly not worked in a programme at the gym.
Really, you should look into Vince Gironda techniques and see how he advised the lateral raises and the upright rows because that variation really is powerful. How you lift the d/bells on the lateral is how the head is stressed. Make sure the hands are at a 10:2 position on the clock, so the right hand being at 2 and the left being at 10 ... not directly out to the sides as some do them, this hits the traps more and places too much stress on the joint to the elbow and forearms limiting weight.
Dont lift higher than your head either. Just stop at the shoulder height otherwise again you work the traps in the higher range.
For a condensed Shoulder workout I would simply choose the laterals, upright rows and shoulder presses. You got your PUSHING & LIFTING components in for the shoulders and than the laterals are delt with. As well if you like you can try laterals on cable pulley machine which really can take it into another league.