The lovely shampoo bar I made 2 or 3 years ago has become my luxurious body bar - only for my skin, not for my hair. At first I loved it, but it was very hard to rinse out of my hair. I don't and won't use a hair condition to rinse my hair (I break out in hives when I do, so I just don't.) I have done the ACV rinse route in the past and don't need to go there again, because it just make my scalp more oil. So I just stopped using it as a shampoo bar.
Then I watched a youtube video of the making of liquid soap containing lanolin and red turkey oil, among other things, and the soaper said it was going to be so good for the hair that I decided to try it, too. So I made that soap after making sure I bought all the ingredients she used and followed her video and the follow up video (it was in 2 parts) very closely to get it right. Well, it's fabulous as a shaving soap, which is all I used it for now. I love it for shaving my underarms and my legs, because I never nick myself with a razor since I started using this LS. But for hair shampoo, it just did not work out at all!
My lovely waist-length whitening blonde hair began to look and feel like straw in very short order, in spite of the lanolin included in the recipe. My husband tried it, too and he liked it at first, and for a bit longer than I did, but after a couple of months he said his hair felt different and he quit using it as a shampoo as well. Of course he doesn't have a lot of hair, just a bit around the edges, and he keeps that hair cut short. So even a person with very short hair (also of the blonde turning grey variety) did not find lye soap at all acceptable.
Luckily I stopped using it soon enough to not totally ruin my hair, but some people have actually had to cut their hair after using lye soap on their hair, so I feel fortunate.
Others do have more positive experiences with lye shampoo, and Zany, another member here at SMF reports very positive results. She will surely reply with her experience and some suggestions. So perhaps it may work for you as well. My suspicion is that hair type and certain other unknown genetic factors perhaps, plus other adjunct products may contribute to others success. I don't really know for sure because I only have my own experience.
We do also have very hard water, but use a water softener. I do add EDTA to my soap to help reduce soap scum, but suspect soap scum was part of the problem that made my hair look and feel so dull when I was using the lye shampoos.
Since I just stated getting into soap making that also means I'm using my own or other's homemade lye based shampoo/body bars to wash my hair but we have hard water and my hair is left greasy as sin, believe this is due to hard water and my hair use to being stripped then coated in demithicone (think that is spelled right or at lest close to) and is transitioning to the shampoo bar/soap but I will admit I miss the smell that shampoo's and conditioner's left on my hair.
I know some people use water and EO's in a spray bottle to refresh the hair but can you use FO's (fragrance oils) in their place?
Again my question is can I make a hair refresher with fragrance oils.
My concern about using Fragrance Oils in a spray on the hair would be not only concentration, but content in the FO. Same with EOs, I guess. Alcohol or phthalate, just a couple of examples. With some research, you can find phthalate-free FOs, though. Still what other ingredients are in FOs you will never know because a complete ingredients list is covered by the 'Trade Secret' realm.
Also you'd have to take into account the safe usage limits for each FO (just as you would with EOs) because it will come into contact with your skin; i.e. scalp, face, neck, shoulders, wherever your spray or your hair touches.
Women have been spraying perfume on their hair for centuries, so I don't think using Fragrance Oils is a new concept.
Your hair may be greasy from added oils and butters in the "Soap" you are trying to use for hair. Soap is NOT SHAMPOO and not good for hair. You will be much better off and your hair will like you much better if you learn to use a nice surfactant based shampoo bar. Even a quality surfactant based m&p bar is better for hair. Here is a link for a shampoo base 
