Mix It Up Meaning
(idiomatic) To compete vigorously, to quarrel, or to fight physically.
Example: 1920, F. Scott Fitzgerald, This Side of Paradise, ch. 2:
He would have felt like an irate ticket-holder at a prize-fight where the principals refused to mix it up.
(Can we verify(+) this sense?) To engage with people, relate to people.
2010 Meet the Press interview with Colin Powell, speaking of Sarah Palin:
Q. What is her impact right now on the Republican Party, and does it bother you?
A. She's a star. Why--it doesn't bother me. I mean, she is out there mixing it up, she's conveying her views, she's animating people to come forward and participate in the political process.
2015 BBC interview by Jon Sopel with Barack Obama, 24 July. Answer to a question about his trip to Kenya:
This one's more business. You don't have the time to travel. You don't have the time to, ah, mix it up.
To create one or more variations of the usual way in which something is done.