Converting Script RenderTexture and Blit code to Graphics.CommandBuffer: Need Help

I have the following script that works perfectly to render everything a camera sees onto a smaller RenderTexture and then Blit it to the screen -- for mobile performance:

 #pragma strict
 
 import UnityEngine;
 import UnityEngine.Rendering;
 
 var myCamera : Camera;
 
 @Range (0, 3)
 public var downsample : int;
 
 private var myRenderTexture : RenderTexture;
 
 private var width : float;
 private var height : float;
 
 function Start () {
     width = Screen.width / (downsample + 1);
     height = Screen.height / (downsample + 1);
 }
 
 function OnPreRender() {
     myRenderTexture = RenderTexture.GetTemporary(width, height, 16);
     myCamera.targetTexture = myRenderTexture;
 }
 
 function OnPostRender() {
     myCamera.targetTexture = null; // null means framebuffer
 
    Graphics.Blit(myRenderTexture, null as RenderTexture);
 
     RenderTexture.ReleaseTemporary(myRenderTexture);
 }
 

It works perfectly as I intended. Now I'm trying to accomplish the same thing using the Graphics CommandBuffer but can't get anything to work.

Can someone help translate the code to CommandBuffers?

Thanks in advance. Manny