Update as of three-four weeks ago:
I use a couple tablespoons of baking soda (I totally dilute the BS in water and use a sport-style bottle to squirt it on, then I massage my scalp well before rinsing VERY well), which I'm sure is more than I need, and I just spritz on the ACV after I get out of the shower. I have long, thick, curly hair, and I learned not to put the BS more than a few inches from my scalp; my hair was SO full of static! What I read said most people use about 1 tablespoon of BS to a cup of water and 1 tablespoon of ACV to a cup of water. My hair has been AWESOME. It's soft, smooth, mostly tangle free, static free, easy to braid. In fact, three or four days in was the first day I'd worn it any way besides down, and I'm usually in a pony tail by then.
Update two-three weeks ago:
There is a residue on my hair for the first time since that unfortunate bath tub washing. I thought I was really thorough with my rinsing, but apparently not. My hair's not too different otherwise, though, still easy to manage.
Update one-plus week ago:
My hair was greasy very early in the week. I attribute that, at least in part, to my hair being past the too-long point. My hair always reaches a needs-to-be-cut point where it is very tangly and greasy and yucky no matter what. Since I was growing out my hair for Locks of Love, I wasn't getting it trimmed. My scalp also protests violently at this point, and my scalp was itchy and raw.
I finally got a chance (thanks, Mom!) to go get my hair cut. My scalp already felt better immediately after the cut, but it still had its issues. The next day I washed it my hair, and it felt GREAT. The day after that, however, I felt a bit of residue again. My hair was a little stringy looking but not too bad, again.
I decided to wash it a bit early because the residue was causing some scalp irritation. I couldn't rinse out the BS at all. My hair was sticky. I thought maybe it was just my hands feeling funny, but I touched my hair with my totally-clean forearm, and it became sticky. I tried to rinse more, but nothing was changing. I knew vinegar would probably take care of it, but shampoo was right there, so I used it. My hair felt wonderfully clean. The next day, however, it started to get oily. Two days later (yesterday), my scalp started to itch. Today my scalp is a raging mess, and my hair is an oil slick.
I definitely can't go back to shampoo, but I can't use BS, either. I found a site that lists alternatives for the BS and ACV, so I'll try something there in place of the BS. I'm bummed, but I'm determined to find something because shampoo is DEFINITELY not me-friendly.