How to instance meshes that are vertex painted in the editor?

Hey all,
I’m making some foliage. They’ve been imported from SpeedTree.
I’ve setup a master material and instances so that I can vertex paint some variation and moss on the plants.
Now how to I instance these using the foliage tool such that they use the vertex painted data?
The usual workflow is to drag and drop meshes from the content browser but these meshes don’t have any vertex paint data on them.
Please point me in the right direction to get this working.