"Picado" Any reason to rest thumb on 6th String ...?
https://youtu.be/khHUnE3C_is?t=1m54s
Size and thickness matters
https://youtu.be/iQghhyf898s?t=12m4s
How Paco de Lucia sanded his fingernails + left hand proper length
https://youtu.be/C_6Cdc2Zcdc?t=1m17s
Nails length affect picado posture, angle of attack and speed
https://youtu.be/NfSyCOFpf5M?t=14s
Superlative secrets on picado
https://youtu.be/jewga7jspyI?t=6m3s


Picado posture applying multiple vectors of force
https://youtu.be/WdS0bBpRDRo?t=1m27s

Picado posture applying multiple vectors of force (Wing Chun)
https://youtu.be/WdS0bBpRDRo?t=14s