Hey beaky,i'm not sure if these rub on transparent decal paper would suit the problem but it may be a solution for the black and it would be very thin,shame you cant paint the gold on and then put the rub on decal over the top,also the new mimaki commercial inkjets print gold,silver and white nowdays and most print shops have them i'm sure they could print it on decal paper,worth asking anyway.
here is the link for the decal paper supplies
http://www.decalpaper.com.au/products/rubon-decal/clear/
