Do I pre-treat from top to bottom, or from bottom to top? What about re-treat?
You should be pre-treating (that’s the overnight one on dry hair, where you wash as usual in the morning) from the bottom up by working in your pre-treat product – massaging upwards, and then smoothing in a downward motion, layering with water. Focus on needy areas and ends (which are always needy) first and go up as far as you need to; there is no need to pre-treat your scalp. Try to learn how to tell by feel where extra is needed and not over help areas where that extra care is not necessary.
Re-treating (after the shower on wet hair) is done in the same way, from the bottom up. (No need to re-wet hair or apply in layers.)