Concentrated bleach can indeed work wonders, but it takes a long soak, one has to keep case metals out or it gets eaten, and alas, the treatment seems not to work in every case (or, should that be, "on" every case?). The metal issue affects what you can do with some bezels, e.g., where there is metal attached to the plastics. A little surgery might be needed in these instances.

My best success has been with a Q650 bezel, which came out of the bleach after a week or more looking spanfire new. It had previously been a sorry sight, yellow and forlorn. I have also had good luck with a DuoDock lid, which I renewed a side at a time. It took weeks, but the results were excellent.

I reckon that a minute quantity of the surface can be dissolved at a uniform rate using this method, which, if smelly, is at least cheap. But it has to be concentrated bleach.

There was a post from the UK, I believe, some months ago which described use of another off the shelf product for these same purposes. I can't seem to find it, though....