How can I fix my weight painting? Duplicated and flipped object

I was trying to get around an issue where I couldn’t apply a mirror mod because the mesh had shape keys, so I duplicated the object (1 half) in object mode, flipped it on the X axis, joined it in object mode then merged double verts. The mesh is fine and I even textured it BUT… This has resulted in one side of the armature controlling both sides of the mesh.

I made a copy of the mesh/armature before screwing this up so I have the weights/etc from that still, if I can use those somehow. Help me!

I guess this should work:

  • copy the object
  • rename the vertex groups of the copy (the ones which refer to non-central bones)
  • flip the duplicated mesh and join the objects

The result is that you have different vertex groups for left/right, which you can match with the left/right bone names.