Steve

Any composition you create in After Effects (well, almost any) can be used as a mask for another layer or set of layers, using the Matte function. If you wanted to use your animated swirls to reveal the wall texture behind, rather than appear on top of it, it’s very straightforward:

Instead of setting the layer’s blending mode to Overlay or anything else, go to the Matte settings next to the Blending modes, and assuming your texture is behind the swirls composition layer, select the texture and from the Matte options, choose “Alpha Matte” which will use the layer above it (the animated swirls) as an animated mask to reveal the texture

Let me know if you have any questions on this, or can’t find the Matte options easily?

In the list of tutorials I have for Layers (http://www.layersmagazine.com/author/steve-holmes), there was a specific one about Mattes and Masks I did a few years back. That might give you some more in-depth explanations of how the various mask and matte features will help you out:
http://www.layersmagazine.com/aftereffects-tutorial-matte.html

But the basic form is that your animated comp sits on top of the layer you wish to reveal through that animation, and you tell the layer beneath to use that top layer as an alpha matte.

Hope it works for you, let me know if any questions

Steve

Thanks