I know this question being asked a lot of times, yet I couldn't find a way for my solution.
The black box is the mask(name "Oil Masking"), and the layer below is the full oil inside the bottle("Oil on Bottle").
I want to show the remainig oil inside the bottle, minus the black box & the "block-outed" oil, so it will look like the oil is not totally full.
I tried many blending type but it just won't work. (I'm not totally understand this part) I just can't figure out how to solve this problem...
Help is so much appreciated.