Mix the amla powder in coconut oil and leave it for a week.. then apply it to the roots.. the herbs shud just be applied to the roots and not the entire length of the hair.
Amla, shikakai, reetha and methi (powders) can be mixed in water and applied to the roots.. soak u're hair completely because when the herbs dry-up they tug on the hair.. so wet u're hair completely and use a very mild shampoo (u dont need it since reetha causes lather) and just apply conditioner to the ends of u're hair.