I am a Sales Consultant, not a Sales Man
Unfortunately it seems are stuck in 70/80s selling. There are many Carnegie, Tracey, Covey principles that are still apt. The vast majority of this is manipulative and though may work in a boiler room/hardsell transactional sale has zero clout today. Buyers are simply too smart.
SPIN selling? Couldn't be further away, time to visit the drawing board me thinks