I don’t think this is an exception. Record yourself doing these things and critique yourself. It’s not as valuable as having multiple people critique you, but it’s not less valuable than having one other stranger critique you. Until you gain a certain level of competence you’ll know where and how you suck.
I’m currently learning bass guitar and recording myself has been incredibly valuable for seeing and hearing things I don’t notice when I’m playing. I think it’s also sort of closed the gap between what I think I sound like and how I actually sound when I play. (I’d recommend it even if you get a teacher.)
my only teachers have been online videos and web pages. I can’t see how a teacher can add value here. If I got one, I’d most likely be learning the teacher’s way. I’m finding a lot of value in hearing multiple POVs, trying it all out, finding what works for me and whose opinions I should value.
The article says teachers are faster, but I can evaluate online video sources much faster and more easily than I can evaluate teachers.
I might not learn faster but I certainly learn more and at a deeper level, because my mind is engaged in every part of the process.
As an aside, I think teachers often gloss over things that they think don’t matter right now. You’re getting a short cut, but you either miss out on something or later have to learn how that thing connects to what you know. Often, I find taking a moment to learn a little bit about that thing can aid you on your overall goal.