Just use keywords like super long hair, big hair, very long hair, and then the ethnicity, hair color, location, lighting, and if you want photorealistic images, use words like hyper-realistic, natural skin, and use names of cameras like Nikon, Canon, Sony, etc. This is valid for Midjourney AI. Also mention the shot type and angle. And the best results always come after improvising on the first results. So try newer versions and enhancements of the first results until you get your perfect picture.