The problem with big companies is that they set up training sessions that last for a week instead of mentoring sessions that last for an hour. Once a week everyone should meet with their mentor for an hour and talk.
And what do they talk about? A good mentor knows that the mentee drives the conversation. Maybe the mentor saw the mentee make a mistake and could comment on it, but younger people know when they are struggling and are always ready to learn if they respect the person who is helping them.
Formal training really has never been a good idea. The army does it for new recruits but they do it because they are trying to create soldiers who don’t think and just follow orders. At the higher level of army training, at the Army War College for example, officers sit around and talk.
Tell everyone they need to spend an hour a week mentoring and an hour a week being mentored. Let them say officially whom they have chosen. Create a culture where mentoring is the norm.