Bingo on the mentoring. I had a guy that we hired at my last job that I spent time working with (about 10-15% more than I would normally spend on the job), mainly because the biggest thing he (and other juniors) need to learn is not only how to find your own answers, but also how to keep track of time and not go on wild goose chases.

It's one thing to just say, "google it", but you need to also point people in the right direction if they are struggling. I would know how to solve some of these problems, but I'd rather I teach someone else how to fish, and maybe leave a trail of clues and breadcrumbs, if the problem wasn't time sensitive.

You also have to be available (and not be annoyed) to explain higher level architecture and other concepts too. I'd make sure I often would include him in the design process of a system, including explaining the high level architecture, all the way down to the lower level pieces, over the course of a project.

It's a lot of work, but has huge benefits. The guy I was helping was progressing really well, but then said employer did something REALLY stupid, which basically was the beginning of the end for both of us there.