I work in a video store for almost 5 years, it helped me a lot. First you are more confident, because they want something from you, not the other way around. Second, you have to talk a lot. Talking much helps. When I'm not working for a week or so, I really feel that I need that "training". But that's not a work thing. I spent 2 days at home in a row, not leaving the house. The third day I felt like I stutter a lot more than before. So talk talk talk, that's the medicine.