In fact the EFX version of our synths has no difference from the Intrument. You must use it exactly like you use the instrument, so you must trigger the envelopes of the MMV, and use the external input in place of the oscillators.
Plug the external input in your filters, modulators, etc, and at the end trigger the envelopes via midi.
You also need to instanciante a midi track and assign it to the MMV EFX to do so.