According to The Beauty Department, using a foundation brush correctly involves applying foundation from the nose outward in the shape of a star. Foundation brushes are key to proper application of foundation because they press the foundation into the skin rather than just dusting it on top.
The first step in using a foundation brush is to squeeze a dollop of foundation into the hand. Approximately a nickel-sized dab will do. Placing it into the hand allows the foundation to warm up slightly, making it easier to apply.
After dipping the foundation brush into the makeup, the next step is to draw a line from the center of the nose to the center of the forehead. Then, add more foundation to the brush and create more lines in the shape of a star, drawing from the center of the nose to each cheek, then from the nose down to each side of the chin. After the star is in place, use the foundation brush to distribute the foundation evenly across the face.
The final step is to brush up the remainder of the foundation from the hand and apply it to the neck, blending carefully to make sure there is no visible makeup line between the face and neck. If wearing a high-neck top, it is important to blot the makeup on the neck to avoid staining the material.