Hi Matthew, I want to share some thoughts and comments. I've heard about and tried the nail filing method on the strings before but didn't find it superior to using an ordinary file and sand papers. My reason is that we don't stick to an only angle of plucking but change it accordingly to the techniques, i.e. rest stroke, finger alternation, tremolo, etc, so if the method were to create the "ideal" nail shape for the filing angle, it wouldn't for the other playing angles. Secondly, the method is actually trying to create a shape of minimum resistance of the string to the nail, which can be good or bad for the sound. I think if you understand your nails enough and you know what to expect from them, a normal file still does the work well. However it's worth to give the filing-on-the-G-string method a try and see if you like it.
Some minor comments to the videos. I like the natural sound of your playing as in the second video more than the processed ones in the other (too much reverb to my ears). One more thing, in the second video, at 2:30 you criticize rotating the elbow away when going across the fretboard, exaggerate it and demonstrate the correct technique very well. However when speeding up, when you exert less conscious control on the arm and the fingers, you do rotate the elbow
. You can compare the slow version from 6:03 to 6:11 and the faster version from 7:07 to 7:10 to see that. I don't say doing it is right but it reminds me of the debate "knuckle vs middle joint" in another thread, where some famous performers demonstrate one thing and actually do the opposite in real playing.
Other than those, the videos are really helpful, especially the practicing musically. I think many people are putting too much weight on practicing mechanical techniques, but forgetting they're trying to make music as well.