Is it harder for junior leaders to seek out a potential mentor or is it harder for senior leaders to find a mentee?

The onus is on the junior of the two (I guess the mentee...is that a word?). You can't go looking for someone to mentor. It doesn't work like that. I guess it can, but that means someone is walking around going, "I have all this information to share and I'm looking for a special snowflake on which to impart this knowledge." A leader should provide it to everyone in their daily business. A leader of character and commitment will continually strive to be a positive influence in the careers and lives of their subordinates. It is only after a subordinate has seen something they admire in a senior leader can the unofficial process of mentoring begin. I separate this relationship from general leadership because it is, indeed, a more intimate relationship. Usually it begins with the subordinate asking questions which are professional in nature, but are more pointed than your general passing of information. This process goes on and in time, the junior person comes to the senior person as often as they want to ask questions about the profession or to solicit advice about how to progress in their career. Sometimes, they may ask for an endorsement or intervention on their behalf in a process. It isn't something which should be sought for. It is something that should mature over time. I guess using a more formal structure could work, but it would feel like an arranged marriage. I am sure arranged marriages work out sometimes, but it has to be uncomfortable for a long time.

I don't believe mentorship can be lumped into a program. The Soldiers I was blessed with the opportunity to serve as a mentor too, sought me out, picked my brain, opinions, and used me as a sounding board for ideas and solutions to hard issues. I'm humbled and honored to have some who still keep in touch. People don't have to like you, leadership isn't about popularity it's about being fair honest, tactically / technically proficient. Some of the best leaders I had, I didn't especially like, but respected their expertise, and knew if I asked an opinion on an issue I was trying to resolve regardless of what it was they would point me in the right direction and I trusted their advise. I think its more important for leaders to be approachable than likable.

It doesn't have to be a 1:1 ratio.

I've commented before but I had dozens of mentors when I was a young troop. Sometimes it was 15 minute conversations. Sometimes it was 2+ year relationships.

When the Adj explains what he actually does, that's mentoring. When the Comm PSG gives a hip-pocket class, that's mentoring. When you know who to go to to ask the right question, or better yet who to send your guys to when they have a specific question, that's mentoring.

When we "formalized" the mentorship program, we did ourselves a disservice. Our immediate supervisor is always our mentor, as are our many of our peers who we interact with daily. The amount of knowledge we absorb just working around others is the goal.