Most of the times they take turns for every track, cuz it gets from the left mixer to the right one and back and forth again (if I'm right).

​@@laurensvanaalderen9307 DJ here, yeah that's basically spot on how it works. Easiest way to put it, individual songs in each wheel, the 4 vertical sliders in the middle at the end is the volume for each wheel. As for deciding who does the next mix, usually just on the fly decision. Sometimes do 2 or 3 in a row sometimes not.