Rich,
There are many noise reduction modules available in PixInsight, which are applicable in different situations.
For more specific response, you might want to post examples of the images and noise that you are trying to work with.
In general, one might use MLT on linear images to provide a quick and easy result. Mure is an alternative here.
I would suggest that you use TGV on stretched and composite images near the end of processing. In this case, TGV will sometimes produce remarkable results on your images.
For example, you can Separate the luminance and chrominance operations which is often very desirable.
However, TGV can be more difficult to use, and may require more experimentation on previews to get it to work as you learn how to use it. It is worth the trouble if you want the best results possible.
if you have an image where TGV is not working for you, you can try MMT on a stretched image.
In all cases, you need to pay attention to the masks and parameters to apply the noise reduction to the places you want in the right amounts.
Eric