What you may need to do for your mixing of textures is to "stack" the blenders.

The basic idea is that a blender node has three inputs: A, B, and Control.

If you want to combine X, Y, and Z, you use one blender node to combine X and Y. and a second blender node to combine the output of the first with Z.

The basic trick you're using is often called a Second Skin, and some figures have "spandex" morphs that can work well with that, with morphs at wrists and ankles that align with material boundaries, and give an edge to the fabric area.

Let's say that X is the base skin texture, Y is an overall mesh pattern, and Z is the solid clothing. Control-Y and Control-Z could be transparency maps. I try to think of transparency maps as a special sort of control-map.

Blender 1 uses Control-Y to blend X and Y, making X_Y

Blender 2 used Control-Z to blend X_Y and Z to produce the final texture.

If you want to experiment with math operations on control maps, it makes more sense to think of a transparency map as an opacity map. Here's why.

The math functions treat white as 1 and black as 0. But black is 100% transparent, and white is 0% transparent. Use opacity, and the percentages and the numbers match up.

But be warned: I'm the sort of person who will do horribly complicated things with math nodes, And then skips all the complexities by using long, thin, tiles as stripes.