There is another recent post by Darthbray that might be worth your while:
Rather than using a library such as controlP5, Darthbray wrote his/her own Button class. An array is made to hold 50 of these, which are created (and added to the array) a little bit later.
Similar to Darthbray’s Button class, you could write your own SliderSet class that groups together a slider and its associated buttons.