At the moment you would indeed have to use this mask as @AMISUCK mentioned. In 5.4 or 5.5 you can also use vertex attributes instead of vertex color. And you can paint the mask directly in the ML Deformer viewport in 5.5 as well.
At the moment you would indeed have to use this mask as @AMISUCK mentioned. In 5.4 or 5.5 you can also use vertex attributes instead of vertex color. And you can paint the mask directly in the ML Deformer viewport in 5.5 as well.