I have tried a script like this for the past year for engineers at around the Senior engineer level. I have been really happy with the results so far: the idea of "leadership mini-vacuums" makes growth here fairly approachable. The steps are small and people can choose to start with the step with which they are most comfortable.

EM: "Think about the best run project you've ever seen. What was the name of that project?"

IC: "Probably it would be the Foo project."

EM: "And what about the Foo project did you really like?"

IC: "Everything about it. There was a clear plan of what to do, the sprint planning meetings were well organized, the project excited senior leadership, and we even presented the project in an all-hands meeting."

EM: "All of the things mentioned are the result of someone being a leader on the project in a small way. Every time your project is missing something from the Foo project, there is probably a 'leadership micro-vacuum' that you could volunteer to fill. For example, you could: run the sprint planning meetings, create a project plan with milestones and deliverables, or send out weekly status emails to senior leaders. There are all sorts of little ways you can help, so you can start with just one and pick your favorite."

IC: "I'm worried that I won't do a good job on that, though"

EM: "In fairness, you probably will not do as good a job as the Foo project on your first time.       You'll be slow, or make mistakes, or maybe just not be as polished. But if you never accept even a temporary drop in quality, you can never iterate and improve. Since I know that you are trying a new thing, I will be supportive to help you avoid mistakes and forgiving when you make them." 

IC: "I still feel weird doing some of those tasks."

EM: "Unfortunately, you will have to push through the discomfort the first few times. One thing that helps me is realizing that "the uncomfortable feeling I have when I am doing something new" is the feeling of growing. The other thing that helps me is to do it the first few times with some who has done this before, like the Tech Lead."