Q: Nimo asks, 'Can I give up shampoo entirely in place of ACV rinses?'
A: It is a personal decision. Shampoo is a powerful cleaner capable of stripping hair of the oil and associated dirt attached to the oil. Yes I am saying that this stripping action is beneficial if you want clean hair. To see further details on why surfactants can be good - go here
There is no research that I have found to indicate that vinegar can clean hair (that is dissolve oil like surfactants in shampoo do). It may have antifungal and antibacterial properties though which may make it useful (see this post).
Research would indicate that if you want your hair to be clean (i.e oil free) use a shampoo with a powerful surfactant such as SLS. If you are happy to have not entirely clean hair (i.e almost oil free but not quite) then choose a shampoo with milder surfactants such as cocobetaine.
Q: Yvonne wants to stretch her hair washes to two times a week and asks ' Is it better to sneak in a co-wash when my scalp gets too oily or should I rather use my hair tonic (which contains a lot of alcohol) to refresh my hair between shampoo washes?'
A: I am not a fan of alcohol based rinses (personal opinion!). I have searched quickly for some research but I have not found anything particularly conclusive for hair. There are studies on skin which indicate that alcohols can strip away oils (good for cleaning) but may also disrupt the skin cells (not so good for maintenance).
I am pretty certain that alcohols can dehydrate skin and hair too (but I need to find some sources to back this up!). Therefore I will save this question and report in more depth later.
Personally, I think that washing your hair is better than using an alcohol based tonic. If you do not want to entirely strip off all the oil , then as you say, a co-wash in between may work well enough.
**Edit: See updated information (i.e scientific fact) on alcohols here **
A: Ok the easy answer first, conditioner is water based and will be more attracted to the surface of hair if it also has water. First rule of chemistry, like attracts like. Therefore, conditioner on wet (damp not soaking wet) hair is probably the way to go!
The second part is really a question of preference and time. I am assuming that you want to 'deep condition' and you do not like shampoo therefore are substituting it with a co-wash. I would say in this scenario, you would still follow the shampoo and condition rule which with your preferences would be co wash and then deep condition.