Clothing Blendshapes

I have set up a system to adjust the Blendshapes of an avatar with sliders. I also have clothing items that will attach to the Character object and copy the bones to animate the same as the avatar. My question is, do you need to also make Blendshapes for each clothing item in an external modeling program like Blender or Maya that match the avatar Blendshapes, or can you just have the clothing models copy the Blendshape deformation. I am just hoping I don't have to create Blendshapes for each clothing model.