Walking itself enables many of the small muscles that are important for proprioception. In addition, the deep, stabilizing muscles are mainly used. Walking carefully without neck brace and on many different grounds for example street ground and then sand or forest ground teaches your body and your spine to balance and stabilizes your whole spine. It is also very gentle on your joints and easily accessible and practicably for most people.
I am currently using a Fitbit tracking device to count my steps for personal motivation. I can program it with a daily step-goal and try to reach it. Of course that does not work every day (not even half the time I reach my goal) but it helps me to stay active even with all my symptoms and to not decondition completely.