This range is best used on clean hair, so start by washing yours. Then, take the American Crew Precision Blend colour that best matches your natural hair, and mix it with the developer in a small bowl. A 1:1 ratio is best, and for hair that is 2.5cm long, you’ll probably need about 20g of colour. Apply to your hair evenly (be sure to wear gloves and old clothes) and try and keep your application time under 4 minutes. Then, let the colour develop for a further 5 minutes, rinse well, and use conditioner.