I don't know what your definition of good programming is, but you yourself are the single best resource for teaching it. General, high-level considerations aren

I don't know what your definition of good programming is, but you yourself are the single best resource for teaching it. General, high-level considerations aren't going to cut it in this scenario. You need to take his actual work and turn it into units of learning by showing him how you would have implemented something differently, asking him how he arrived at specific implementation details, quizzing him on long-term support issues that could arise, etc.