Youtube?  Seriously?  Video tutorials are the least effective method of teaching ANYTHING if you are expecting long-term knowledge retention.

Using videos to teach a highly visual activity? Come on.You should contact Gnomon and tell them to stop using such an inappropriate medium for teaching and revert to books (better if handwritten on parchment).

In the educational field we have about 20 years worth of empirical evidence that it IS the least effective for long-term knowledge retention.  Proving that video works as a teaching tool was the holy grail for about 20 years - the problem is the data doesn't support the thesis - as an entire generation of Doctorial candidates has proven. Companies do them because they are easy to make - there isn't a lot of time or effort to put into them compared to other teaching methodologies

It is all part of the Some people learn by doing, others learn by listening, other learn by watching nonsense that came out of the educational establishment post WWII.  It's a great theory, but the problem is there was no data to support it - and there still isn't.