As Otis said, 'try a lil tenderness'. It's amazing how much people can soften when you give them attention, affection, and your own calm energy! Sometimes I think people that are prone to yelling is because they have a complex about not being listened to so if you just start off by giving them your undivided attention, it may catch them off guard, but they won't have anywhere to yell really?
When all else fails in and things get heated, always bring people back to the goal. What have we set out to do and how can we make it happen, even with these new problems? Put feelings/who's at fault/frustration aside and treat everything as a creative problem that can be solved with a creative solution. <3