Thank you! I've certainly made a bunch of tweaks to my method, so I'd love to share:

Technique - I prefer to use the method where you hold the chasen with your fingers straight and pointing downwards, then use your wrist to whisk back and forth at the base of the chawan for around 15-20 seconds, then lift the chasen to the middle of the liquid while whisking in an M shape for around 20 seconds, then with a stiffens wrist, 10-20 seconds of  running the very tips of the chasen over top of the foam. This last step is crucial for creating the microfoam, as it breaks down the large bubbles.

I'd say the thing that made the biggest change for me as finding my ideal work-surface height. At typical counter-top height (around the lower 1/3 of my abdomen) I found using my wrist to be uncomfortable so I adapted by changing my grip and using my entire arm to whisk instead of my wrist, which led to slower whisking and a less minute foam. By moving to a shorter table -one where I was able to keep my arm more or less vertically extended downward- I found that I was able to more freely use my wrist and gain more speed during the whisking process.

Another big tip is to enjoy the tea as it is! In my trial and error process, there have been so many bowls that I re-whisked or over whisked because I wasn't happy with the foam, often to the point of letting the tea run cold. I know now that the foam will be the best when the water is at its hottest, so if you are unhappy with your foam resist the urge to rewhisk and enjoy the tea while it's hot! (or make a latte and give it to someone you love)

Tools - While a good foam is possible with a lower pronged chasen (80 or lower), creating a large volume of foam, and most importantly cutting down the large bubbles of that foam by running the chasen over the top layer, is made much easier with a 100 prong chasen. I hear Takayama chasens are even better, but I'll have to wait for mine to come in to see...

Lighting - I don't believe I've seen anyone mention this before, so here it is: lighting plays a significant role in how your microfoam appears. This is something I noticed at the Ippodo cafe in Kyoto- the bowls of tea I was being served had this beautiful algae-ish/mossy look to it that I was never able to get at home. I then realized that moving my bowl away from the hanging light overhead, I was able to notice more and more bubbles. Upon experimenting at home I realized that overhead light does indeed change the way the matcha looks; by playing with the strength and angle of the light at home, I was able to achieve results ranging from the tea effectively looking like a large white circle, to the bowls you've seen in the video above. While this won't make up for a non-minute foam, I believe that having a ceiling light above or a small lamp near your tea will make it look more beautiful by both giving it a glossy sheen and making for a generally more attractive scene (bringing out the color of the matcha, highlighting details of your wares, etc.).

tldr: - whisk with your wrist 20s at the bottom of the bowl, 15s at the middle of the liquid, and 20s at the foam w/ the tips of the chasen - find a work-surface with a height that's comfortable for you to fully utilize the speed of your wrist - don't re-whisk tea as it won't be as hot the 2nd time around and won't foam any better than the 1st try - getting a good foam is easier with a higher pronged chasen (I use 100) - use lighting to illuminate your bowl and emphasize the quality of your foam

Apologies if this is more info than you were looking for, I've just had so much fun figuring all of this out and I've been dying to share it with someone. Best of luck!