I think your inclination that less is more is probably the right one.
A lot of people use a “stencil brush” or similar large brush. From what I’ve been told, you can also (gently) use a microfiber cloth.
Avoid handling the gold with bare hands, and make sure your hands are clean if / when you do have to touch it.
https://harpcolumn.com/forums/topic/cleaning-a-gold-harp/ — this thread may have some info as well
Karen Gottlieb has some good general cleaning tips here:
https://www.kgharp.com/tips-for-harpists-cleaning