The Camelot actress, who starred alongside Brand in 2007 film St Trinian's, also revealed that the comedian did not "flirt" on set.
Egerton told Yahoo: "Russell was amazing with all the kids - everyone from eight to 15!
"While we were waiting around between takes, he would just carry on spouting all these amazing jokes, being very witty and just improvising on the spot, he had everyone in hysterics."
"I've worked with him twice and he was very very loud then he can be quiet. He's very holistic; he would go off and do yoga at lunch time."
She went on: "He didn't flirt with me! He is very polite and respectful to all us ladies but I'm sure he is a very good flirt."
Sympathising with Brand's popularity with the media, he added: "I would hate to be papped, I feel really sorry for those people. It must be hard and upsetting.
"It's different for people who go on TV shows, but some actors are exceptionally private."
One recent report alleges that Brand's split with Katy Perry was due to the fact that she was not prepared to start a family with him.