My roleplaying group is composed of four friends who roleplay using roll20 as our board and Skype to handle our voice communications.
I have one player who is used to roleplaying only in text and doesn't feel comfortable using his voice due to lack of experience, and another who doesn't think they're smart or witty enough to speak out loud (again, a rather inexperienced player). The other two are roleplaying veterans who have no qualms roleplaying out loud.
I want to make these early experiences fun for all my players, but I also want the two newer players to get used to roleplaying aloud, because that will allow the game to move at a brisk pace. (In the past with a different GM, some of the players have complained about how slow the story moved and text roleplaying became really awkward)
My question: how can I ease these two newer players into roleplaying with their voice and not just the written word? If it helps, I'm running the DnD 5th Edition Starter Set quest.
EDIT: This group of friends has known each other for a while -- the two who are less experienced are just new to the idea of roleplaying in voice. We chat all the time on Skype about non-roleplaying-related topics.