Purpose of Pre-pooing?

[Buttercreme]

I just recently discovered co-washes, and can't believe I waited so long to try them. I love them and so does my hair(daily). Super moisturized hair.

But why pre-poo?
Is it done with oils or conditioners?
On wet or dry hair?
How long should I pre-poo?

 

[Meli]

I just recently discovered co-washes, and can't believe I waited so long to try them. I love them and so does my hair(daily). Super moisturized hair.

But why pre-poo? depends on what you need---you can use oil (amla, evoo etc) as a prepoo to help relieve the hair of dryness or a light protein treatment (ORS Mayo or Motions CPR) to help reduce breakage

Is it done with oils or conditioners? either
On wet or dry hair? it works for me on damp hair....but either wet or dry hair
How long should I pre-poo? I prepoo my hair with Amla Oil overnight...if I have less time I do it an 30 min up to an hour. No set time. I do mine for a while because I am not using any heat...just wrapping my hair up with a showercap and towels.