"He's doing well," he found himself saying, fingers dancing along the edge of the oni mask hidden within the folds of his overcoat. "Once he was able to see that fire is only dangerous if you let it, he was able to bend with ease."
That was simplifying it a bit, but it would do as an answer. He didn't really feel up to talking about how well the Avatar's training was going. On one hand, he was bending really well for a beginner and Zuko was impressed with that, but on the other hand, he was a bit jealous. For Aang was doing far better within his first week of firebending than Zuko had within his first two years. He remembered the time he tried to out-best Azula in front of their grandfather, Fire Lord Azulon, and had fallen on his face in the attempt.
...your sister was born lucky; you were lucky to be born...
He shook the thought away, fingers tightening around the edge of the mask.