My balance is no longer a major issue. I am working on improving it. I do work on my core.
I consider my balance issues to be a neurological issue. I balance on both feet or one foot and focus on one point. Then I move my eyes back and forth in focus and same up and down. I also move my head to change what I am focusing on. The principle is to exercise the feed back between my eyes and feet. I also move my arms to affect my balance. I do sometimes close my eyes.
I do not have a regime as I find no comfort in being anal/ a good boy. I do it ESO every so often. I do it when standing in line, waiting or pumping fuel into my car.
This is my own concept and not blessed by any experts or proved other than my evaluation. I came to it from my knowledge base as a skier, golfer and walking steel beams as a connector.