I think there is a fundamental problem in using a word as educational tool if that word is not clearly defined and understood through experience by the student. The fact that we are using a Japanese word, indicates to me that the whole thing is inscrutable.
I believe that if a person has an understanding of "ki" and wants another person to understand it, the only way is to have that person do things that engender a "ki" experience, and then point to that experience and say to the person, "What you are experiencing is ki."
To go the other way, that is start with a verbal concept of ki and then endeavor to have a person experience it, is near to impossible. I have heard someone describe ki as like being in love, inexpressable in words, but when you're in it, you know it.