'Alpha Over' overlapping layers wrong... Really noob question

So I am working on this art style that involves overlaying several layers and applying a drop shadow so it looks like a 2D layered image… but for the life of me I can’t remember how to apply a simple alpha over and have it work properly.

So here is the end result I want, for example:

Simple enough. I want the skin to be on a separate layer so I can apply a different effect on it in the compositor, and then put the layers back together.

I know there is a method… but I can’t remember it for some reason. I looked online and can’t find a solution.

Let me attempt to break the render to show you what I mean:

Obviously just alpha overing the layers doesn’t work… I need to subtract the alpha’s or something… And i don’t remember how!

Someone help! I am having such a stupid moment right now! -.-

Either put each arm on its own layer or use a mask layer to mask out the body for the arm render layer


mask.blend (96.9 KB)

Mask layers, that’s what it was! Thank you so much!

Here is the result I was going for, if you are interested