Two articles:

https://www.fs.blog/2012/10/velocity-of-skill-development

Summary

1. Problem: It’s hard to get the quantity of repetitions you need for feedback with the variety of situations you need to develop improvisation.
2. Solution: You can tinker with the environment to force people to make faster decisions, increase the number of repetitions, and force a velocity that increases the variety or situations a player can practice. When developing a soft skill you want three things: 1) variety; 2) reps; and 3) feedback.

https://www.fs.blog/2012/07/what-is-deliberate-practice/

1. Another way of interpreting deliberate practices:  Deliberate practice is characterized by several elements, each worth examining. It is activity designed specifically to improve performance, often with a teacher’s help; it can be repeated a lot; feedback on results is continuously available; it’s highly demanding mentally, whether the activity is purely intellectual, such as chess or business-related activities, or heavily physical, such as sports; and it isn’t much fun.
2. Designed to Improve Performance: The word designed is key. While enjoyable, practice lacking design is play and doesn’t offer improvement. Expertise, as the formula goes, requires going from unconscious incompetence to conscious incompetence to conscious competence and finally to unconscious competence. *
3. Repeat: Repetition inside the comfort zone does not equal practice. Deliberate practice requires that you should be operating in the learning zone and you should be repeating the activity a lot with feedback.
4. Feedback on results is continuously available: Practicing something without knowing whether you are getting better is pointless.
5. Mentally Demanding:  “The work is so great that it seems no one can sustain it for very long. A finding that is remarkably consistent across disciplines is that four or five hours a day seems to be the upper limit of deliberate practice, and this is frequently accomplished in sessions lasting no more than an hour to ninety minutes.”
6. Ben Franklin, an interesting example
7. The Role of Solitude: Deliberate Practice is best conducted alone for several reasons. It takes intense concentration, and other people can be distracting. It requires deep motivation, often self-generated. But most important, it involves working on the task that’s most challenging to you personally.