It's been a long time since I've done one, but I am do, so I need a refresher too but from what I remember and did it was about 1-2 tablespoons of apple cider vinegar (some use other types or whatever is on hand) to one cup of water and I use this as my co-wash and let it sit for a couple minutes, then rinse.
Something else that I haven't tried is the lemon-aid where you take the juice of 1 lemon and equal amounts of conditioner and use that as a co-wash to clarify.
Cowash - No Poo, Suave Coconut
Conditioner - One Condition
Leave In - KCKT
Gel - KCCC at the moment
I use 1/4 cup apple cider vinegar mixed with 1 cup of water (if I recall correctly, that's the recipe from the Curly Girl book). I use it once per week by spraying it into my hair until it's saturated. That takes about 1/4 of the mixture. I leave it in for a few minutes, then rinse, condition and style as usual.
Couple of inches past shoulder length 3A. Shampoo every 3rd or 4th day w/ baby shampoo; Tigi Fashionista conditioner; back to Condition 3-in-1 mousse . Alternate days water rinse, conditioner and mousse.
When I do this I mix about 2 tablespoons ACV with 2 cups warm water; dip ends in, then pour slowly over hair (don't get it into your eyes); swoosh it all around then rinse. and I do this between Co washing and conditioning.