Unity2D: Frost Effect Animation

Hi, I want to know is there a way of using Mathf.SmoothStep to control the float of a variable? You see I downloaded this package on unity assets store and created a IEnumerator OnTriggerEnter2D (in a new script) to control the effect once my player hits an orb, making it slow down but now I want to add an animation. Rather than having it appear of the screen and then disappearing, I want to make the frost effect slowly come in, kinda like controlling the frost amount in the inspector. It is possible, because I tried doing it like this:

(This is attach to orb)

 // Use this for initialization
 void Start () {    
 }
     
 IEnumerator OnTriggerEnter2D(Collider2D other)
 {
     if (other.tag == "Player") {
         //frost.enabled = true; 
         GameObject.Find("Main Camera").GetComponent<FrostEffect>().enabled = true;
         FrostEffect.valToBeLerped = Mathf.SmoothStep(0, 1f, FrostEffect.FrostAmount);
         yield return new WaitForSeconds (1.01f);
         FrostEffect.valToBeLerped = Mathf.SmoothStep(1, 0, FrostEffect.FrostAmount);
         GameObject.Find("Main Camera").GetComponent<FrostEffect>().enabled = false;
     }
 }

But it's still appearing automatically rather than it slowly coming in like an animation. Anyway this is the frost effect script I downloaded from the assets store:

(Attach to the main camera)

 public static float FrostAmount = 0.3f; //0-1 (0=minimum Frost, 1=maximum frost)
 public static float valToBeLerped = 0;
 public float EdgeSharpness = 1; //>=1
 public float minFrost = 0; //0-1
 public float maxFrost = 1; //0-1
 public float seethroughness = 0.2f; //blends between 2 ways of applying the frost effect: 0=normal blend mode, 1="overlay" blend mode
 public float distortion = 0.1f; //how much the original image is distorted through the frost (value depends on normal map)
 public Texture2D Frost; //RGBA
 public Texture2D FrostNormals; //normalmap
 public Shader Shader; //ImageBlendEffect.shader
 
 private Material material;

 private void Awake()
 {
     material = new Material(Shader);
     material.SetTexture("_BlendTex", Frost);
     material.SetTexture("_BumpMap", FrostNormals);
 }
 
 private void OnRenderImage(RenderTexture source, RenderTexture destination)
 {
     if (!Application.isPlaying)
     {
         material.SetTexture("_BlendTex", Frost);
         material.SetTexture("_BumpMap", FrostNormals);
         EdgeSharpness = Mathf.Max(1, EdgeSharpness);
     }
     material.SetFloat("_BlendAmount", Mathf.Clamp01(Mathf.Clamp01(FrostAmount) * (maxFrost - minFrost) + minFrost));
     material.SetFloat("_EdgeSharpness", EdgeSharpness);
     material.SetFloat("_SeeThroughness", seethroughness);
     material.SetFloat("_Distortion", distortion);
     ///Debug.Log("_Distortion: "+ distortion);

     Graphics.Blit(source, destination, material);
 }

Thank you. :)