Lori.
Is this a scenario in which someone is accosting you or harrassing you. Is it a situation where you feel threatened?
Based on the info you gave, you stated the "hand on the shoulder" with elbows locked. Obvioulsy they are larger and stronger.
I am an advocate of always assuming a neutral position with palms forward and fingers below the chin. This does incorporate the natural fighting stance but without "posturing". The legs remain in the natural fighting stance while the arms and hands display neutrality.
I am going to subtract the escape factor and just get to the meat.
I would take the path of least resistance and by feining neutral and utilizing peripherals you should know where that is.
You can rotate outside and project through or you can rotate inside and project through. The nearest target is the groin. If you rotate inside and take the groin you can get under thier base and dump them by pulling out the leg from behind the knee cap with the hand thats not clutching the crotch. You would be simultaneously lifting up on the groin to take thier weight off thier feet while clutching the leg and pulling it into your hips. he falls on his back and head and it took no real strength to put him there...just gravity and physics and reaction to spinal reflex.
If you rotate outside the target is the same but you will end up behind them after the rotation and projection through them so dumping them will be a bit different but the concept remains the same.
Keeping your base is paramount and taking thiers away is equally important. Your base should consist of your inseam length. Mine is 32" so there is a 32" space between my feet in every movement while I am standing.
Rotation, of course is a circular motion wether is 20 degrees or 360 degrees. Rotation is paramount
Projection is putting yourself through them by replacing your body with where they were.
It may not make sense but its the best I can do without visual reference.
or you can just lock the bad guy's arm & break it if necessary. but you know, whatever's easiest.
jf