I think your entire post is a fine example of why you're having difficulty dealing with "sales guys". How to deal with "overly confident" people? You mean assh

I think your entire post is a fine example of why you're having difficulty dealing with "sales guys". How to deal with "overly confident" people? You mean assholes? Because when a person is "overly confident" about something they know very little about, that's the definition of an asshole. And there are a lot of assholes in sales. Being an asshole in sales makes you successful. Nobody wants to sign a contract with someone who's not sure of what they're doing. The key characteristic of an asshole is "fake it til you make it". In other words, act confident in a field even if you know absolutely nothing about it until you do know something about it. The best way to deal with someone who's faking it is to simply call them out on it. But doing that is a bit of an art. Rather than simply pissing them off, guide them to the right conclusion. Even though they're "faking it", they still do want to learn how to do it right, even if they will never admit it. Him: "This button should be over here." You: "Ok, I like your idea, but what if X and X happens. We should add what you said, but do it here." Compliment them. Tear them down. Suggest a better alternative, incorporating some minor insignificant part of their original idea. Keep repeating until you get the desired outcome.