All my colorants are NB...pigment. They all hard-pack. Fluorescents are the worst for it. I had been using a Stainless Steel Rod Epoxy Spatula but have went to a piece of 3/16" Brass Rod with a Rounded Tip. The Brass Rod is plenty strong and the Round Tip doesn't scratch or cut plastic bottles. All my bottles have a 5/16" Stainless Nut in them, also. After I stir and loosen the settled pigment (it's about like cold peanut butter), I shake 'til I'm convinced it's ready...premium thinking and premium efforts are most of the components in premium products. Drink plenty water before You start. Like some good days and some not-so-good days in fishing, this is all part of it.