The difference between using a lip brush and directly applying lipstick by hand is mainly reflected in the clarity, color uniformity, makeup effect, hygiene and naturalness.

Clarity: The lip brush can more accurately outline the outer contour of the lips, especially for the corners of the mouth and other details of the processing is more accurate, suitable for people with thin lips, can avoid the problem of painting out of bounds, so that lip makeup more clear and delicate.
Color uniformity: the use of lip brush can avoid lipstick stuck in the lip line, making the color more uniform, especially for people with poor lip condition, lip brush can bring a more uniform application effect.
Makeup effect: lip brush is suitable for creating exquisite makeup effect, such as lip bite makeup, etc., which can achieve the ideal effect through multiple superposition. And directly by hand coating is more suitable to create a natural, fuzzy "kiss lip" effect, the edge is not obvious, it looks sexy and natural.
Hygiene: It is more hygienic to use a lip brush because it can be cleaned and avoids the problem of bacteria on your hands. However, applying lipstick directly by hand may cause hygiene problems, especially when there are more bacteria on the hands.
Naturalness: Apply lipstick directly by hand because the temperature of the fingers will make the lipstick slightly emulsified, making the color look more natural, suitable for people who pursue natural makeup effects.
To sum up, the choice of using a lip brush or directly applying lipstick by hand depends on personal needs and preferences. The lip brush is more suitable for people who pursue refinement and uniform makeup effect, while directly applying by hand is more suitable for people who pursue nature and convenience.