Teach a real peer and let them push back

Explain to another person who can ask questions and say "I don't get it."

Why it works

A live learner provides what no rehearsal can: real-time signals of confusion that force you to re-explain, find another angle, and repair your own model when your first explanation fails. The social pressure to actually be understood raises the bar above "this makes sense to me", and reformulating on the fly strengthens and reorganizes your knowledge.

How to do it

1. Find someone unfamiliar with the topic and teach them a small piece of it.
2. Invite them to interrupt with anything unclear.
3. When they get confused, treat it as data about your understanding, and re-explain differently.

Evidence

Peer-tutoring studies repeatedly find that tutors gain academically, often as much as or more than the tutees, with the act of explaining and responding to questions credited as a main driver. (rct)

Much peer-tutoring research is in classroom settings with confounds (motivation, selection); the directional benefit to the tutor is well supported even if exact magnitudes vary.

Common mistake

Picking an audience who already knows the material, so they never get confused and never force the re-explanation that does the learning.