We did this at my job. We just bought the bundle of vouchers. We used an online training platform (several out there). I met with the group 2x a week for 30 minutes and reviewed concepts and questions. I tried to review items I felt would be important for them to understand. We did it for two months. I started with 10, and 3 dropped out. 6/7 passed the last person, never took the exam.
I advise them to take the exam as soon as the training is over while the material is fresh. Let me know if you have any questions.