If I want a color that Rustoleum doesn't come in, and I have the color made, i.e., the store has to mix in pigments and then SHAKE IT to mix the pigments thoroughly into the base, how long will I have to wait before I can expect the bubbles in it to dissipate and I can roll it on? Can I just stir it instead and expect the pigment to mix well enough? Anyone with experience with this? Thanks