OK- I've found a seller for this in the UK. Is it just a case of brushing on, leaving a few minutes and rinsing off, or does it need to be added to a specific solution to use? I may just go with a black wash of paint....Yes I used the Aluminium Black Metal Finish from Birchwood Casey in the little blue bottles. Worked like a charm.
I have seen as well that is used to touch up scratches on guns, but basically it will blacken any aluminium surfaces, so might as well use it