"1 gram = 15.4323584 grains.
Looks like a 'minims' is a drop."
60 minims = 1 dram
8 drams = 1 fl. oz.
I think a drop is too large. Thanks for the formula.
One thought, if you are going to paint brass, "sweat" the moisture out of the metal first with a propane tourch and have the metal hotter than room temp. before painting but below 95*F. You will be suprised how much water will come out of the metal, it stops the paint from sticking over time.
Good luck with it.