How to manage shader with script

Yes, you can change the material shader at runtime, here is a way to do it. (Assuming the gameobject to which the script is attached has a mesh renderer component)

 void SetSpecularShader()
     {
         //Get the mesh renderer
         MeshRenderer m_Renderer = GetComponent<MeshRenderer>();
 
         //Get the specular shader
         Shader m_StandardSpecular = Shader.Find("Standard (Specular setup)");
 
         //Apply the shader
         if (m_StandardSpecular)
             m_Renderer.material.shader = m_StandardSpecular;
         else
             Debug.Log("Check shader name");
 
         //Assign shader values....
 
     }

Hope this helps...