He is a confidence man. He will do you before you know where you are.

他是一个骗子，当你清醒过来之前他已经把你骗了。

You follow the simple instructions step-by-step and, before you know where you are, the finished article stands before you, complete in every detail.

你只要一步一步地跟着简单明晰的指示做，还没等你反应过来，成品就会出现在你面前，所有的部分一应俱全。