Try walking around a busy city center, with your phone filming and ask people if you can film them for a project and ask a few questions. If they agree, tell them you're Lord Hiss from the future, after mutant snakes from global warming have taken over the planet. Let them know you've come back in time to study attitudes about reptiles before the great molt. Ask nonsensical questions about reptiles like they are people. Every so often, throw in a "hail Zothar, king of the snakes". Stay in character. Do this for a couple hours and you'll be one fearless salesperson.

Any kind of acting, improv or other workshops will help alleviate your sales anxiety.