Here is a simple exercise called Bucket Game. It is primarily used by marching bass drummers to practice splitting rhythms between two people, but can be a good practice tool for any percussionist. I recommend starting with the top part, and practicing two bars at a time with the metronome. Once you have mastered A to B on the top part, try the bottom part two bars at a time (still with the metronome). Then find a buddy and have them do the same thing, and eventually split the rhythms. Once you both master both parts from A to B, move on to the next section.
Free PDF and video: