To the point - to gain successful sales means that the sales person has to use effective people skills, backed up through supported decision making processes. Backing management allows the new sales person to reach a decision on their own, implement that decision, take responsibility for the outcomes from that decision, move forward having learned from the actions and counter reactions.
Primarily for the sales person to obtain the help that enables them to further develop confidence, communicate well and establish a rapport with other people, an initial stepping stone should be implemented. This could be as simple as using the introductory and handshake phase to garner the control of the situation. to have this control stabilised and past through to others the whole time you are their selling.
Once the people skills go up, the sales go up. Confidence is given by both parties. People like the way business is handled. They become relaxed. The people skills go up to a new bench mark level.