1. He's an old hand at managing difficult clients.

他是处理困难客户的老手。

2. The veteran detective is an old hand in solving complex cases.

3. Don't worry about the machinery; the technician is an old hand.

4. She proved to be an old hand during the emergency situation.

5. The coach relies on the old hands to mentor the newcomers.

6. As an old hand in the business, he knows how to negotiate effectively.