The hidden curriculum consists of the unwritten rules, unspoken norms, and field-specific insider knowledge that are essential for student success but that are not taught in classes. This phenomenon is pervasive in university computing majors because some students come in with more prior childhood exposure to computers and technology culture. Some learn aspects of the hidden curriculum from mentors, but not everyone has access to a good mentor. This paper presents a thesis for how to scale up access to the hidden curriculum to reach more students: We propose that a peer-written guide with an informal, relatable tone that focuses on local context can emulate what a peer mentor does by emotionally resonating with students and motivating them to take concrete action. As a case study, we implemented this thesis by creating a mentoring guide for interdisciplinary computing majors at our university, which has received over 2,500 online views so far. Interviews with 17 students and a survey of 112 students showed that our guide’s relatable tone could emotionally resonate with students, that it boosted some readers’ self-confidence, and that it inspired them to take actions such as creating a project portfolio. Then based on this thesis, we developed a five-step design workflow to help others create similar guides for their own local contexts, with recommendations for 1) setting up a mentoring guide, 2) needfinding, 3) creating, 4) distributing, and 5) maintaining such a guide.