Cat & Camel. I find it preferable when returning to cat to lift your head up slightly past neutral, and if you can, roll back onto open hips into child. As your head touches the mat go back into cat and repeat, do this for five rounds once a day, preferably in the morning after sleeping and getting stiff. Really focus on rounding your tailbone down and tucking your chin on camel, and the opposite on cat. I find this provides a good basic flow and helps reinforce both poses instead of alternating holding patterns and is really great for the lower back.
It's kind of hard to answer this because you seem to be talking about external rotation as if it's a single, fixed quality. There are a number of joints which externally and internally rotate. It's a better idea to focus whether or not you have flexibility and stability through a specific range of motion. For example, in the squat you want to maintain external rotation of the hips (knees pointing out). If your knees begin to point in during the movement or if you have tightness in your hips then you may want to look at improving your external rotation.
Try foam rolling your upper back and shoulders, and maybe see a chiropractor. My right shoulder was pretty weak when my chiro tested it, and my neck was sore and had knots all over it. Then he adjusted my neck -- instantly stronger right shoulder with no pain in my neck.
Wendler lays out a few options in the 5/3/1 for Powerlifting FAQ for dealing with extended time off the program:
I'll make those changes.