Opaque white is a great paint to use when you want to add highlights and finishing touches to your artwork. It has a high opacity, so it won't bleed into the base of colors, and the viscosity can be easily adjusted by adding distilled water.
You can use a brush or a pen to apply the paint, and when using a brush, you can create different effects by varying the viscosity of the paint. For example, if you want a more opaque look, you can add more water to the paint. If you want a more transparent look, you can add less water. Opaque white is ideal for use with permanent inks and water color, but it cannot be used over Copic markers as it contains pigment based ink.