I just shampoo once and leave it in for about 5 min. However, the back of the bottle says you should shampoo and repeat. Does it really matter, or is that just a way to use more shampoo so you have to buy again earlier?
once should be enough. leave it for more minutes if you can. (can irritate your scalp though). applying twice in the same time is of no use. rather apply every day if you can.