Tinted multiply shader?

I'm currently writing a shader w$$anonymous$$ch will allow me to tint my textured object and overlay my baked shadowing (AO) over the top afterwards. T$$anonymous$$s works as follows:

 Shader "Unlit/AO Overlay"
 { 
     Properties {
         _Color1 ("Color", Color) = (1, 1, 1, 1)   
      
         _Texture1 ("Object Texture", 2D) = "" 
         _Texture2 ("Object Shadow", 2D) = ""
     }
      
     SubShader {    
         Pass {
             SetTexture[_Texture1]
             {
                 constantColor [_Color1]
                 combine texture * constant
             }
             
             SetTexture[_Texture2] 
             { 
                 Combine texture * previous
             }
         }
     } 
 }

The problem is that I also want to be able to adjust the strength of the shadowing using a float, after scouring the internet I'm still not entirely sure about how I might do that. I can use:

 texture Lerp(constant) previous

But that's not quite what I want because - as it's shadowing - I want it to multiply.

Any suggestions would be much appreciated!