Accessing a second texture's offset in a modified sprite shader

Im a complete noob when it comes to shaders. Ive been trying to make an overlay shader for my weapon sprites (so I can add cool animated effects like lightning and fire to them).

This is a modified version of the default shader that I came up with:

 Shader "Sprites/Overlay"
 {
     Properties
     {
         [PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
     _OverlayTex("Overlay Texture", 2D) = "white" {}
     _Color("Tint", Color) = (1,1,1,1)
         [MaterialToggle] PixelSnap("Pixel snap", Float) = 0
     }
 
         SubShader
     {
         Tags
     {
         "Queue" = "Transparent"
         "IgnoreProjector" = "True"
         "RenderType" = "Transparent"
         "PreviewType" = "Plane"
         "CanUseSpriteAtlas" = "True"
     }
 
         Cull Off
         Lighting Off
         ZWrite Off
         Blend One OneMinusSrcAlpha
 
         Pass
     {
         CGPROGRAM
 #pragma vertex vert
 #pragma fragment frag
 #pragma multi_compile _ PIXELSNAP_ON
 #include "UnityCG.cginc"
 
     struct appdata_t
     {
         float4 vertex   : POSITION;
         float4 color    : COLOR;
         float2 texcoord : TEXCOORD0;
     };
 
     struct v2f
     {
         float4 vertex   : SV_POSITION;
         fixed4 color : COLOR;
         half2 texcoord  : TEXCOORD0;
     };
 
     fixed4 _Color;
 
     v2f vert(appdata_t IN)
     {
         v2f OUT;
         OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
         OUT.texcoord = IN.texcoord;
         OUT.color = IN.color * _Color;
 #ifdef PIXELSNAP_ON
         OUT.vertex = UnityPixelSnap(OUT.vertex);
 #endif
 
         return OUT;
     }
 
     sampler2D _MainTex;
     sampler2D _OverlayTex;
     sampler2D _AlphaTex;
     float _AlphaSplitEnabled;
 
     fixed4 SampleSpriteTexture(float2 uv)
     {
 
         fixed4 color = tex2D(_MainTex, uv);
         fixed4 overlayColor = tex2D(_OverlayTex, uv);
 
         color.rgb *= overlayColor.rgb;
 
         if (_AlphaSplitEnabled)
             color.a = tex2D(_AlphaTex, uv).r;
 
         return color;
 
     }
 
     fixed4 frag(v2f IN) : SV_Target
     {
 
         fixed4 c = SampleSpriteTexture(IN.texcoord) * IN.color;
 
         c.rgb *= c.a;
 
         return c;
 
     }
 
         ENDCG
     }
 
     }
 }

How the hell do I access the overlay texture's offset and tiling? Im assuming I have to use a second UV, but I have no idea how to do that. This is probably very simple but Im banging my head against the wall over here