What product has a multi-use brush?

The product that commonly has a multi-use brush is UV gel. This type of product is often applied with a brush that can be used for multiple functions, such as applying the gel to the nail and designing intricate nail art. The versatility of the brush allows for different techniques, including even application, line work, and blending of colors. This is particularly valuable in nail salons where a variety of styles and finishes are in demand.

In contrast, nail polish typically comes with its own brush attached to the cap, intended exclusively for that specific product. Hair color usually involves using brushes or applicators dedicated to the application of that specific color treatment, often to ensure precise application onto the hair. Lotion, while it may sometimes be applied with a brush in certain salon treatments, generally is applied by hand rather than with a multi-use tool, making it less associated with a specific multi-use brush function in the context of cosmetology. Therefore, UV gel stands out as the correct answer due to its multifunctional application possibilities within nail services.