Thanks for the feedback Dunedain, unfortunately I havnt been able to systematize what I'm doing. What I do is push one picture darker and one lighter and then find the right percentage to overlay them (so the darkness and lighness from one picture 'adds on' to the darkness and lightness of the other - the trick seems to be to get it so the two ends align with the mid range so you get a seemless transition in the picture from top to bottom). It works either by having two distinct layers or adding a duplicate layer in another measure.

I have been working on one universal setting for each source, but you could tailor each overlay to each scene to get the most information of whats there at any given time (variables over constants, but establishing a constant first might be a good idea to give a starting base line). I have only tried it with two layers as I am still operating theory-blind - someone who knew how to adjust highlights, midtones and shadows separately might be able to stack 3 or more subtler layers. The thing however with soft undetailed sources it starts to look too "painted" if I start adding too many layers.

As far as I can tell even if the Gout/Blu Ray is damaged it would be possible to paint whats missing back in (if the information is missing it can't be recovered). I tried this with the Luke in the Judland Wastes picture a number of posts back , this was done through thinning out the original picture to thin midtones, duplicating it, then adjusting the new duplicate layer with a different colour curve (so you are not adding back in a linear way but reshaping the boundaries of the original picture - I think [?]). The Luke picture had several layers, I got the 3D effect I was after but it looks too painted.