Add GloomAO-style Intensity Mask to Any Shader?

First off, I don't code. Further, looking around, I'm having a lot of trouble finding beginner-friendly tutorials (or tutorials, at all, really) for programming FX shaders. Sure, I know that it's similar to the DX9 version of HLSL, but that's about where it ends for me. I'm an artist. I understand the basics of things: Depth buffer, vertex vs. pixel shaders, etc. I also regularly mod game rendering, but only through messing with CVars, DLL INIs, and other basic parameters. So, unless there's an easy, hold-my-hand-through-it, introductory explainer for HLSL/FX, I'm not gonna learn it.

So, what I want to do is add the Intensity Mask from GloomAO to other shaders, preferably with an option to blur the edge of the mask. This actually seems like something that should be bog standard in any AO or pixel shader effect. The way it is, I end up duplicating CobraMask to make AOs not effect bright areas. This isn't a viable solution if I want to nest an effect within both a depth and pixel mask (CobraMask doesn't like being double nested)

At any rate, by way of experimentation, what I attempted to do first was simply copy-and-paste the seemingly relevant lines of code from GloomAO into CShade's Solid Color shader within the ReShade Edit Shader option. The result? It did populate the control slider, but had absolutely no effect on the output image. I'm obviously missing some level of complexity here. Something is obfuscated. Any guidance would be greatly appreciated. That, or someone who is an expert could be kind enough to create a baby-steps explainer for getting started in coding shaders in FX. As an artist, if I could find my way into it, I have plenty of ideas I'd love to make into shaders.

Thanks in advance!