Here's the truth, and like most truths it's found by treading long hours in the deep pools of paradox.
The greatest salesman are actually not that great at selling. Rather, they are excellent at empathy. Which can often get in the way of selling. Stereotypical selling is selfish. Period.
But persuading is not selling, while similar they are worlds apart. Selling is about currency. Persuading is genuine, regardless the perceived outcome.
Persuasion can be used in selling, but rarely is. The harsh, but deserved stereotypes of salesman come from manipulation- the imitation of persuasion.
Persuasion can only come from genuine belief. Consider the definition of the word lie, which is to have the intent to deceive.
Persuasion is the intent to believe, for all the right reasons.
This is why Christ asks his followers to preach his gospel "unto the convincing of men". Nephi's purpose was "to persuade men to come unto the God of Abraham and be saved."
The unexpected factor of the truly great salesperson is empathy. Yes, he or she may be gifted with the willingness to be vulnerable and articulate, but the truly great ones are guided by empathy, and they have refined themselves to the development and sensitivity to its influences.
Often falsely accused and wrongly abused the greatest salesmen of them all are the ones genuinely not influenced by the currency of friendship, love, fame or fortune; Despite how beautiful and healthy each of those are in life.
The paradox is that despite their ability to articulately communicate in gifted ways (written or spoken) the truly great would never sell snow to an Eskimo, for one simple reason- he doesn't need it, even though Mr. Eskimo could probably be manipulated to believe that he does.
Its a matter of morals, not money or any other type of currency. It is a matter of the heart. And that can only be discerned by those who are honest themselves, in their dealings.
empathy, who'da thunk it?