slick as a whistle --------- 圆滑（成语）

英文释义
(IDIOM) Describing someone or something that is very smooth and polished.

例句
Our company's best sales representative is slick as a whistle and always knows the perfect way to encourage customers to buy plenty of our products.
我们公司最优秀的销售代表十分圆滑，总能知道鼓励客户大量购买我们产品的完美办法。