Promote any good stuff by them. (Good stuff in general spreads fast automatically irrespective of any push, however, a push always helps).
Organize Bugathons / Testathons (Create opportunities for new testers to really “test”).
Volunteer for pair testing sessions. I have done it with many testers. Some were junior, some were seniors. I learned in both.
Pair learning exercises.
Sessions / Talk on how to brand yourself as a tester.
Guidance on how to create/organize/structure a portfolio.
Sponsor people to conferences. Open doors of wisdom for such talents. TTC sponsored me, I am grateful for that. It opened a lot of things for me about which I was never aware.
The more you know, the more you can know 🙂 If they know this much, I am sure they would pick up the next things automatically.