With regards to peer-programming, or code-reviews, I don't think I could comment. Personally I am a firm believer in test it, and see what works.
This is the main benefit of 1-1 teaching. In a class room setting you can, and perhaps should use "recommended techniques", but 1-1, just do what works for your mentee. Anything you read about benefits of peer-programming or code-reviews is just an idea, which you should be able to verify very quickly with your own student. This trumps everything you might read.
You might find one method works better all the time, or you might find one works better in some situations.
If I may elaborate:
What I believe you are teaching your student, first and foremost, is the ability to observe themselves.
In fact, you may never need to "teach" them anything, if they begin to understand the difference between good and bad, better and worse, themselves, they are well on the route to becoming an autodidact. You do this through testing - not just formal tests, but simple questions too. Your aim is to develop the questioning ability in the student themselves.
I like to think of these analogies: A painter's ability to see is the foundation for their ability to paint. A chef's ability to taste is the foundation for their ability to cook. Both the eye and the palate can be trained.
I will follow your suggestion.
Well, over 6k tutors sounds like you found ways to guide people successfully through the process.
My Question about this is, was peer-programming a standard tool, or just plain code-reviews?