Trimming your mustache won't make it grow faster, but by tidying up thin or scraggly ends, it will give the illusion of looking fuller and more robust. If you do want to improve your facial hair growth, focus on your diet. Ensure you're getting an adequate intake of water, vitamins A, B, C, and E, and biotin to nourish your hair follicles and strengthen hair from the inside. Then regular exfoliating and moisturizing will ensure healthy skin and promote blood flow to the area, improving hair growth.