Which opposing muscles are necessary to work along with a bench press?

Opposing muscles

Latissimus dorsi

posterior deltoids

teres major/minor

Lateral Deltoids

SOME biceps

For bench you need

triceps

pec major

pec minor

anterior deltoids

Try warming up more, you might not be doing enough, and you might be doing it too fast, this happens if i go too fast or don't warm up.

Do dumbell press to strengthen it, it is more flexible of a workout, sometimes barbell hurts some people.

If you have pain I would suggest avoiding any work that involves the shoulder for a week or two. But from there, the opposing major muscles you would want to work are the lats and traps.

You can hit both of those muscles groups by doing pull-ups and any variety of a row such as seated cable row, bent over row with a barbell or using dumbbell.

You are right that proper form and technique are critical in helping to avoid injury. To maintain proper form, always follow these rules:

1. Warm up and stretch the muscles before doing any work

2. Lift using the full range of motion (otherwise you're cheating the muscle from the work)

3. Use slow controlled movements (otherwise momentum removes the focus from the muscles that are suppose to be working to those that aren't. Plus, a slower count helps build muscle. A quick count only works to add strength.)

4. Exhale on the resistance move, inhale on the release

Hope this information helps and good luck in your muscle building progress.

I think that's a bit technical for this forum. Try strengthmill or somewhere.