with a wet finger千万别把它理解成了“手指湿了”。其实是“轻松地、毫不费力地”。
【例句】
He defeated them with a wet finger.
他毫不费力地击败了他们。

Go ahead.You will finish the work with a wet finger.
动手干吧，你会轻而易举地完成这项工作。