Hop inn the time machine and going back 40 years. I am standing in the hall in front of a mirror trying to recall the forehands and backhands I just saw the pros use at a big tournament. I came back from the tournament and got on the court and hit the ball great……and then it went away. This went on for two years before I began using the mirror. I would get into a pose of what the forehand or backhand swing should look like. Then I would close my eyes and bring the racquet to ready positon. When I opened my eyes, my racquet was not where I thought it should be. That is when I realized what I thought I was doing was way different than what I was doing. In 1977 we had no video tape and all we had was reel to reel 8mm film. I actually tried that too and burned up more than a few frames of 8mm film stopping the projector!
Where am I going here? Well you have video on the phone but you have the glass back wall too. Use it to learn faster and accelerate the learning process and use the phone to see what you are really doing.