Depending on the Micron size of the flake it could cause the finish to be rough. In an orange which typically doesn't hide real well (multiple coats needed to achieve full color) it may add some sparkle. If it were me and you had access to a grams scale, weigh out how much paint and flake, take that ratio by weight and mix up a couple of ounces and spray it out and see what you get. My $.02