Two Textures Dissolve Shader (clip & lerp)

Hello! I've been trying to accomplish dissolving one texture to another just like in this Unity video (https://youtu.be/3penhrrKCYg?t=44m50s - watch at 44:50). My textures seem to blend and dissolve together at the same time. I'm new to shaders and I can't figure out how to do it, I would be really thankful if anyone could help. Here is my code :

 Shader "Unlit/Dissolve2Tex"
 {
     Properties
     {
         _MainTex ("Texture", 2D) = "white" {}
         _SecondTex ("SecondTexture", 2D) = "white" {}
         _DisolveTexture("Disolve Texture", 2D) = "white" {}
         _Blend("Blend Amount", Float) = 1
     }
     SubShader
     {
         Tags { "RenderType"="Opaque" }
         LOD 100
 
         Pass
         {
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
 
             #include "UnityCG.cginc"
 
             struct appdata
             {
                 float4 vertex : POSITION;
                 float2 uv : TEXCOORD0;
             };
 
             struct v2f
             {
                 float2 uv : TEXCOORD0;
                 float4 vertex : SV_POSITION;
                 float3 worldPos : TEXCOORD1;
             };
 
             sampler2D _MainTex;
             sampler2D _SecondTex;
             float4 _MainTex_ST;
             float4 _SecondTex_ST;
             sampler2D _DisolveTexture;
             float _Blend;
             
             v2f vert (appdata v)
             {
                 v2f o;
                 o.vertex = UnityObjectToClipPos(v.vertex);
                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                 o.uv = TRANSFORM_TEX(v.uv, _SecondTex);
                 o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                 return o;
             }
             
             fixed4 frag (v2f i) : SV_Target
             {
 
                 float4 texture1 = tex2D(_MainTex,i.uv); 
                 float4 texture2 = tex2D(_SecondTex,i.uv); 
                 float4 dissolveTex = tex2D(_DisolveTexture,i.uv); 
 
                 
                 clip(dissolveTex - _Blend);
                 fixed4 col =lerp(texture1,texture2,_Blend);
 
                 return col;
             }
             ENDCG
         }
     }
 }