This may sound a bit noobish (well of course, it's from me).
As long as I have the kick and the bass, I know how things work. Just equalize both cutting useless frequencies, making room for each instrument. Boosting a little the key frequencies, lowering others, etc.
Let's start to add another kick: no problems. Claps, snares and hats are all fine too, if a good EQ is done.
Problems come when we start to add other percussions. With all those drums there is small room for other percussions (there is still a lot of room for other instruments, though).
What are the solutions?
1) Lowering some channels' volume?
2) Removing unnecessary channels? (2 percussions instead of 3, only claps and no snares, etc)
3) What else?
Basically the question is: when there is no room left for the mix, what do?