I think an overly detailed code walkthrough or lots of reading may be a problematic approach. I favor a higher level overview so information will be retained. Beyond that, methods for helping others help themselves, such as how other developers typically work through an issue. I think the value of more senior people on the team is not their knowledge of the particular codebase (but it definitely helps) but more so how they got to be a senior member. What are their strategies for being effective? These are things that will likely translate across projects in some way.
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