[gashaw]

Prepare a few questions for each trait you care about and then ask all candidates the same (or sample of) questions.

Grade the candidate on each trait based on how well they answered the related questions and pick the best one.

Because you know the questions you can prepare and not be intimidated to ask someone more senior.

For instance:

How to design an app that feeds from two radically different apis? (no need for detailed code)

What perfomance practices they used in library/framework/their own code and why?

What test cases they would write for (a simple) given spec?

Ask them about instances were they mentored/helped/coached teammates.

Good luck.