You might try setting the brick and shingled layers to the overlay blend mode and adjusting the opacity of the layers.
Another way might be to use Filter>Texture>Texturizer where you can load images for texture. The images should be flattened and saved as psds or in the grayscale color mode, flattened and saved as psd files.
In the filter gallery you can combine the textures by making two instances of the filter, one for each texture (bottom of the dialog).
You could also combine both ways above.
I guess it depends on the look your after.
Thanks so much for all your help. I'll take some time to try these techniques and see how they work for me.