I used to be an engineer before I transferred into sales in 1988. I'm guessing you've heard jokes about engineers in sales. Accountants, contractors, PhD's, and lawyers don't have stellar reputations in sales, either. Yet these professions generally are an intelligent lot. They are quite skilled at what they do, since our daily lives may depend on their specific calculations and recommendations.
Here's how I used to sell:
Research the prospect and prepare a powerful presentation that applied specifically to them.