Extras are directed to pantomime so as to not interfere with the sound being recording of the principles on set. But a majority of the time, it’s all pantomiming. It even goes beyond dialogue.
Can I wear jeans to an audition?
You don’t need to dress like you’re going in for a corporate interview here. Your clothes shouldn’t be a wrinkled mess, but you also shouldn’t be wearing business attire to an audition. A good pair of jeans can go a long way, and it’s worth investing in a pair for auditions alone.