"Articulating" is harder than showing with a three dimensional object, of course. I remember in 4th grade, I had my science book open on my desk turned to the page Sister Mary Margaret was talking about. I raised my hand and stood at the left side of my desk when called upon. (That's how we had to answer a question "back in the day".) I tried with my little mind to wrap my head around the concept of rotation and orbiting while looking at the flat two dimensional drawing on the page. I asked, "If the earth rotates around the sun, then why does the picture show the earth on TOP of the sun." Sister Mary Margaret could NOT understand my question, but valantly tried to explain. She just couldn't understand what I couldn't see. I sat down and for the first time in my life, I felt frustrated in school and also felt as if I just couldn't understand science.But the point is, not understanding that concept affected me so much that I remember the details of that day exactly.
So, back to the question of "articulating" this concept:
1. First of all the concept of waning needs to be clear to a person. I always use the sentence "My attention is waning" which I understand to mean that my attention is getting less. So waning is the concept of the light becoming less visible, and thus waxing is the opposite.
2. I'm left handed. When my husband tried to explain the waxing and the waning with the "c" and "d" or whatever trick he uses, I never got it. When realizing that the moon rotates counter-clockwise, I thought, "Ok, I'll say the moon is left-handed". To understand I hold up my right fist in front of my face like the sun,put my left index finger in front of it and rotate it in a counter clockwise position (which is natural for me to do) and when it's rotating in a direction where It's trying to show me it's full self, it's waxing.
3. But STILL I get mixed up. So after looking at your pictures, I watched the video here: http://www.universetoday.com/19699/does-the-moon-r... I kept looking at the video and comparing it to your picture. I told myself to think of the darkness as a curtain on the stage of a performance the "curtain" (darkness) opens from right to left (the opposite way that we read in the Eng. language. As "the curtain" OPENS, the amt of light we see on the RIGHT becomes more and more until we see the whole stage. That whole opening process is waxing. If I get waxing right, I can conceptualize waning. Thank you for this ques., It's getting me closer to understanding. Hope someone has an easier way :) :)