[chasingthewind]

I've been mentoring junior engineers for fifteen years and I've found a lot of techniques that work but there are two ingredients that I think have to be present:

1) You're motivated to help

2) The junior engineer is motivated to improve

I don't think it matters what techniques you use if these two things are in place. If they're not in place then it is very likely not going to pay off regardless of how you approach the mechanics.

Code reviews are critical. Pair programming can be a valuable technique. Going over concepts and best practices can help. Creating a plan for the junior engineer to study the craft. Books like Clean Code can be great at starting discussions.

Good luck!