Bob Sheckley once said that in order to correctly put a question one should know 80% of the answer and I believe he's much more to the point than a Phillip G. Armour.
This whole list of orders is shit. Practice shows folk who have doubts are often the first to be trusted.
Although they are bad commercial travellers, oftentimes, they are most reliable professionals. Fakers and liars are those who put on airs pretending to know all the answers - these people are the last to rely on. On the other hand, 99% of the ignorant are absolutely sure they are not. It's their interference that spoils every good beginning. Examples are many.
Conversely, a good tactics for a professional would be to listen to know-alls' chatter, more that when you fail to see the wood for the trees. Kind of a brainstorm, if you know what I mean.