I’ve been counseled by them what knows to use Testor’s gold paint and a small foam paint roller, no masking required, or a brush after caffeine shakes have worn off
I too use a roller but, used a hard rubber one that didn't put paint down in the low parts. I think the roller I used is for inking blocks for printing.
Both types of small hobby rollers will work just fine, and will be done in a flash. One must remember, these kinds of operations performed during manufacture had to be fast, so the brush method, while it will work, may leave telltale clues.