I cannot reveal identifying details about my experience as a mentor but I can talk in general terms. Let's just say it is a female scholar of Jonathan Edwards working in a University in the Pacific Northwest, but that it is not such a scholar because I have changed the details.
It turned out that what I needed to do was read articles by this person in draft form and make concrete suggestions about improving style and correcting problems in rhetorical presentation, adjusting the quantity of pathos, logos, and ethos (insofar as those are quantifiable entities).
The result was immediate improvement. The articles I edited got much better in subsequent drafts and the person I am mentoring was grateful.
The person's work is different from my own in almost every respect (field, approach, language, rhetorical stance). I know nothing substantive about the subject matter. This made no difference. I might have missed some problem, of course, that a specialist would have seen, but having no stake in the field made it very easy for me to identify any lack of clarity, verbosity, or rhetorical missteps. I have to feel confident that the writer knows his shit, and that my job is to talk about what a non-specialist reader would respond. Someone picking up a journal will not be a specialist in every subfield represented by that journal. I felt that I allowed the writer to bring out her own voice, one very different from my own. I felt completely free of prejudice, never once having to impose my own perspective.
I can work fast, reading an article at one sitting. I know what I think almost immediately, identifying problems without having to overthink. Mentoring is not time-consuming. I could read an article a week with no problem, no effect on my other activities.