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.
3b/a
Cowash - No Poo
Conditioner - One Condition
Gel - Light Defining Gel

Looking to try Devacurl Decadence line next! Can't wait to try it.