Hey!
Whilst I don't have experience with the DWF VI, I have done a VI before with a different firm. A piece of advice that I have is to get accustomed to talking to the screen and seeing yourself rather than another person. What helps is to practise in front of the mirror so that you can control your facial expressions. Be prepared for questions such as "why you?", "why the firm?", "why commercial law?" but don't memorise them because recruiters generally don't like that.
You could also look at resources online, if I remember Commercial Law Academy had a course on interviews. Hope it helps!