I am assuming you mean reverse shoulder surgery. It will take about 6-8 weeks for her/him to be back to training after physical therapy. Given the doctors recommendation, proceed slowly with traditional shoulder strengthening exercises.
My client 76, has been through that surgery after tearing 2 rotator cuff tendons in a fall last year and the initial shoulder surgery was unsuccessful.
In her case, I also found that she was in so much pain, that she almost did not move at all. Her posture deteriorated and she became overall very weak. We work on her core, legs and stamina in addition to some shoulder exercises mostly through Pilates.