I tried the 2D Lipsync Rhubarb animation in this Grease Pencil character.
While it does the heavy lifting, it is not an “instant” solution. You may do the mouths
for the 2D character rather quickly using a .WAV file, but it needs “fine tunning”
to make your lipsync animation more appealing.
With all of that out of the way, check out these and other tips in the
following video:
