Thanks for the comments all. Yeah, the non-metallic metal was only used on the banner where real metal paint didnt seem appropriate, after all banners are made of fabric not metal. Plus the GW paint job seems to use non-metallic gold to do karl-franz's hammer on the banner, so thats why i also did it for the crown on the back of the banner.
In hindsight, i probably could have gone ahead with real metal paint on the banner. Im sure in medieval times gold thread was used in clothes/tapestries/banners all the time.