Teaching method and order.
I was talking earlier about concentration and decisions.
In portrait painting we will meet a number of difficulties such as the composition, the chiaroscuro, the colours, and last but not least, the likeness. If you want to solve all these problems simultaneously, I mean, starting the portrait without any preparation, right from scratch you will have to fight on multiple fronts. Why not separate the difficulties, and attack them one by one especially if you´re a beginner.
Your brain can only make a limited number of decisions before it slows down. That has been proven. So if you break up these tasks you will reduce the number of errors. Right. Now some people say: starting from scratch makes you more open minded, and you will make unexpected discoveries. To a certain extent I agree. But still I say, learn control first, when you have more experience, you can allow yourself more freedom in your approach: Control first, freedom later.
Better to have a controlled run-up than a hit and miss attempt.