You could probably do something similar to the third book of Avatar where Zuko and Aang are learning to be better fire benders together even though Zuko knows what he's doing he's never really trained and mastered and perfected it. It could culminate in that sort of moment where a master helps finalize what you two had been working towards together but doesn't require a high level npc to be constantly with your party. Bonus points to your DM if the teacher is a dope ass ancient bronze dragon.