I assume that you're talking about private one-to-one tuition.
Obviously, this will not help you develop the way you teach groups but it could be a great way to help you develop your exam preparation teaching skills. Working with a single learner can allow you to really focus on the learner's specific needs as they arise, and I think this could be a great way for you to pick up knowledge and skills in a more piecemeal, manageable, and in-depth way.
There is plenty of demand out there for this kind of work, especially if you are open to giving online sessions. I would estimate that over my entire career so far, around half of all the private one-to-one tuition I have given has been for exams, and this has been some of the most satisfying work I have ever done.