Wicked skilz bruv innit?
I am seriously in awe of how you are solving these problems... should you decide you don't want to do home chemistry check out https://www.caswellplating.com/# they have all kinds of plating kits.
I don't know how they do things down there in Napoleon country, but if you aren't hamstrung by the air quality mandates of the Peoples' Republik of Kalifornia the good folks at Caswell will sell you all manner of poisonous chemicals for your electroplating delights.
Keep the updates coming.
BTW - sorry if you have already said - I think you have - but are you running the original 6v system? If so, where did you get your battery from? The Napa 6v batteries I have been buying for our 62 Beetle aren't that great in terms of longevity.