I've been doing acv rinses for almost a yr now. I do them every other wk when I co-wash. I do an over night DT w/coconut oil, co-wash the next day, detangle, rinse, apply acv (I have a 12oz spray bottle that I fill 1/4 of the way w/apple cider vinegar & the rest water), let sit for 15 to 20mins, rinse w/cool to cold water, then style my hair.
I have noticed less scalp irritation, flaking, buildup, defined curls & shine. As far as how much acv one should use, well that just depends on the person & their hair. While I can stand 1/4 of the bottle someone else may need way less or way more.You will have to just do some experimenting on your part and see how your hair responds. However I think its always best to start out w/a little acv &see how your hair responds, then add more if you want then vice versa.