How to make portions of a texture transparent?

Heyo, I'm currently doing a small project involving a few things. I have an image in the background and it is covered by another image. The player uses their mouse like a "brush". As they click drag on the plane on top, the plan is to have the background image reveal itself accordingly sort of like a lottery scratcher. Is there a way to make portions of a texture transparent based on the brush stroke? I'm also all ears to totally new approaches than the one I currently have! Thanks!

Unity version: 2020/3/25f1