smooth operator

noun2

1. •
   A person who accomplishes tasks with efficiency and grace, especially one with verbal skills who is persuasive in interpersonal relationships, negotiation, etc.

   • In Washington he has earned a reputation as a smooth operator who can handle lobbyists, bureaucrats and even Congressmen, with a cool head. — 1986
2. •
   A skillful, manipulative person, con artist, or clever scoundrel.

   • He plays the hospital administrator, a fast-talking smooth operator who cons patients and doctors alike. — 1972