How do I rotate finger joints using controller input?

Suppose I have an index finger composed of 3 cubes which all contain Rigidbody which have isKinematic set to true. In a hierarchy they are the parent and children like this cube1 -> cube2 -> cube3

I want to control how my finger curls using the controller which outputs strength in range 0-1, e.g. the ArrowUp button. Put simply, if I hold the up button, all the cubes would rotate around Z for 60 degrees. And if I release the button, it would rotate back to 0 degrees. (All degrees in between 0-60 are valid when the up strength is between 0-1)

How do I rotate the finger while also making it collide with other objects? For example, you could use the finger to kick a ball.

If I don't care about the collision, I can just use transform.Rotate(0, 0, buttonUpStrength) in the Update() function and attach this script to all the cubes. But I care about collision and rigidbody.MoveRotation() is not enough because the position of each child will stay at the same absolute position when I use it. So I need to use rigidbody.MovePosition() to move the children relative to the parent also. But it's still not enough, the animation is not smooth, I want the animation to be smooth so I'm thinking that AddTorque() might be a better way out, but I don't know how to use it as isKinematic=true objects cannot be used with AddTorque().

What is a smarter, simpler way of making the finger kick a ball, without the finger being pushed back by the ball?

This is how my finger looks like, it's just a cube. This is my script, that I attach to all cubes, in the inspector, I set cube1's angle to be 60. The children will just copy the angle of the parent:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class TestJointRotation : MonoBehaviour
 {
     public float angle;
     private Rigidbody rb, rbParent;
     private Vector3 originalPos;
     private Quaternion originalRot;
 
     void Start()
     {
         rb = GetComponent<Collider>().attachedRigidbody;
         if (transform.parent != null)
         {
             rbParent = transform.parent.GetComponent<Collider>().attachedRigidbody;
         }
 
         originalPos = transform.localPosition;
         originalRot = transform.localRotation;
     }
 
     void Update()
     {
         if (rbParent)
         {
             angle = rbParent.GetComponent<TestJointRotation>().angle;
         }
 
         var rotation = Quaternion.identity;
         if (rbParent) 
             rotation *= rbParent.rotation;
         rotation *= originalRot;
         rotation *= Quaternion.Euler(0, 0, Input.GetAxis("Vertical") * angle);
         rb.MoveRotation(rotation);
         if (rbParent)
             rb.MovePosition(transform.parent.TransformPoint(originalPos));
     }
 }