Be sure to use momentary ("Flash") style buttons otherwise your DMX values will remain at 255 until you clear them, and you won't be able to fire your same button twice.
Example: Using a DMX channel to fire your next clip. You'll want to flash that DMX value to 255 to fire that button. If it's held at 255 and you try to push that button again, it won't fire as the value is already at 255.
Other than that, it's pretty basic, just like MIDI.