using drag and drop to change MovieClip layer's opacity

Hi all, I am creating a simple game in Animate. I want to be able to pick up(drag and drop) a MovieClip(1) which when moved over another MoviClip(2) will change the opacity of the topmost layer in MovieClip(2). I know I do not explain well.

The game will involve washing dishes or a car. As a graphic of a 'sponge'(clip-1)  is moved over a representation of dirty dishes or a dirty car-bubbles animate from the 'sponge' and depending on how long the 'sponge' is held over the dishes(2)then the opacity of the top layer (which will represent dirt) will drop to reveal a 'clean' layer beneath.

I have seen this exact thing done in the app my boo where the creature is washed with a sponge.

Thanks in advance guys.

Peace - John