How to Set Skinned Mesh Renderer from Parent Object?

As title. I have a child gameObject called head, which has a Skinned Mesh Renderer attached to it. I want to set its Smoothness (floating point) value.

My trying currently:

character.transform.Find("head").GetComponent(typeof(SkinnedMeshRenderer)).Smoothness = valueValidated;

parentObject.transform.Find(“CHILD_NAME”).GetComponent().material.SetFloat(“_GlossMapScale”, yourValue)