real-time mentorship
Quality of your mentorship skills can only be gauged real-time.
Researchers and entrepreneurs fight on the frontiers and frontiers are by definition unique territories beset with unique problems. Therefore, you can not mentor these people in pre-packaged formats (e.g. lectures) in artificial environments (e.g. classrooms). You need to go to the battle with them, shoulder-to-shoulder.
What distinguishes the mentor from the mentee on the battle ground is the speed of problem solving. Mentor too learns alongside the mentee since the problems at the frontier are always unique and new. His only difference is that he learns faster.
Mentee who sees the mentor in action learns better since learning is essentially a mimetic process.