Hello HB
I developed cording in my right arm - like you, right down to the wrist, and very painful. The best exercises for me were the stretching ones, where I had to reach to 'touch the ceiling' and then slowly twist my arm. I could gradually increase the distance. I also walked up the wall.
I tried to find a cording physio and went to the Royal North Shore Hospital in Sydney. The physio I saw there had never heard of it (she was fresh out of college) but the head physio had and asked her to do lymphodema massage! (?) I didn't go back. But the stretching exercises they gave me in hospital did the trick. It went away in 6 weeks.
Best wishes
Jenny