Surface shader appropriate for fur?

So... I've decided to throw myself into shaders and try to implement a fur effect (actually, grass), I've seen some code which works by doing 5-60 passes, improving quality as it goes.

I'm completely unfamiliar with Unity's approach to shaders, so am unsure if a surface shader is appropriate?

The manual says (my emphasis):

Which seems promising. I'd like to template/define a method for what each pass looks like and call it a variable number of times (I'd like the number of passes to be configurable if possible). Step one is to get multiple passes working, however, I seem to be failing quite hard. I've got two issues which may be related:

> I can't work out how to execute a variable number of passes
> I can't get multiple consecutive CGPROGRAMs to blend their output

My current test case to figure this out is:

Code (CSharp):

1.  
2. Shader "Custom/Grass" {
3.     Properties {
4.         _Color ("Tint", Color) = (1,1,1,1)
5.         _MainTex ("Color (RGBA)", 2D) = "white" {}
6.         _Fade ("Fade", Range(0,1)) = 0
7.     }
8.     SubShader {
9.         Tags { "RenderType"="Opaque" "Queue" = "Geometry+1" }
10.         LOD 200
11.  
12.  
13.  
14.         Blend SrcAlpha OneMinusSrcAlpha
15.  
16.         CGPROGRAM
17.             #pragma surface surf Standard fullforwardshadows
18.             #pragma target 3.0
19.  
20.             sampler2D _MainTex;
21.  
22.             struct Input {
23.                 float2 uv_MainTex;
24.             };
25.  
26.             fixed4 _Color;
27.  
28.             void surf (Input IN, inout SurfaceOutputStandard o) {
29.                 fixed4 c = tex2D (_MainTex, IN.uv_MainTex);// * _Color;
30.                 o.Albedo = c.rgb;
31.                 o.Alpha = c.a;
32.             }
33.         ENDCG
34.  
35.  
36.  
37.         CGPROGRAM
38.             #pragma surface surf Standard fullforwardshadows
39.             #pragma target 3.0
40.  
41.             struct Input {
42.                 float2 uv_MainTex;
43.             };
44.  
45.             fixed4 _Color;
46.             float _Fade;
47.  
48.             void surf (Input IN, inout SurfaceOutputStandard o) {
49.                 fixed4 c = fixed4(0,0,1,_Fade);
50.                 o.Albedo = c.rgb;
51.                 o.Alpha = c.a;
52.             }
53.         ENDCG
54.     }
55.     FallBack "Diffuse"
56. }

I'd expect that as _Fade is varied, the shader would fade between the input texture and blue, however I just get solid blue.

What am I missing? Are surface shaders just not appropriate for this scenario?

Thanks for any help you can provide.