Hi
The suggestion post you are refering to is too old. Denoise profiled had many changes in 2019 and 2020 
You can take a look at my tutorials on youtube if you want to see how you can use it.
If you want to use several instances, you can, even without using blend modes (apart from lowering opacity, blend modes are usually unneeded for denoising now that wavelets support correcting luminance and color noise separately). You can set the wavelets to denoise only color noise, and a non local means instance (before or after) to cope withe the remaining noise.
Could you post an example raw file so that we can experiment on it?
Also, the use of the module is way easier once a camera is supported, you can see how to create a noise profile for your camera here: How to create camera noise profiles for darktable
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