How can you temporarily parent certain vertex groups to bones? Something like the "Child of" constraint but with vertex groups instead.
I think the hook modifier is what you're after.
Without any parent relationship :
- Select your mesh
- add a hook modifier
- in Object, select your armature
- in Bone, select the "parent" bone
- in Vertex Group, select the "child" vertex group
- You can now move the bone and animate the strengh of the modifier:
here's also a good tutorial about it.
You can parent using the following steps:
- Select the mesh then select the armature
- ctrl+P then parent with empty groups
After that once you want to clear the parenting:
- go to the vertex group menu in the properties panel
- Click the small down arrow
- Clear all vertex groups