It's possible to animate a mouth using meshwarp in AfterEffects, however if he's not already puppeteered opening and closing his mouth in the correct way, I don't think it will look convincing. Perhaps if there's a shot of him which happens to match up with what's being said (or can be made to match up by masking in the mouth from different shots) it could provide a good base for then applying the same techniques as he's used already.

Of course, by ROTJ, it's possible Ady will have progressed to using a full CG mouth replacement depending on what he wants to accomplish.