I found a method recently that allows you to create morphs using bones that you can use as an alternative to using the vertices method.
I've been converting some models from XPS to MMD, which usually have fully articulated bones for the face. I've found it easier to work with moving the bones than the vertices for most facial movements, but was using a method that was tedious and made adding the facials difficult.
I just recently discovered this method so I might post an update if I found out anything more, but if you have any questions feel free to comment.
Tutorial on making morphs using the vertices method: https://www.youtube.com/watch?v=Yxv6flp5yuQ
