I think there's nothing better than practice :)

And in case you want to get familiar with the profession, I could offer to try Talk to Ri app in about one week) (it's the product I'm working on, it hasn't launched yet though and its content isn't updated for now). https://itunes.apple.com/us/app/talk-to-ri-business-english/...

It's actually more for learning English for tech, but we will have a conversations trainer, including tech sales manager program)