I might have something that helps because I have extremely dry hair too. I drink plenty of water and I eat really healthy food and I couldn't figure out why my hair was sooo dry.
I accidentally stumbled upon my technique trying to DT my dry hair and realized once or twice a week wasn't cutting it. I was bagging my hair for hours and it would still be dry and of course after taking hours to completely dry my hair (LP) it felt like I over did the protein. I found two conditioners that seemed to help for a while but I had to constantly rotate them due to my hairs pickiness.
But what really helped and how I found this technique was because I was in a hurry and couldn't DT but my hair was so dry I had too. So I decided to do a "quick" DT in the shower, I co washed with tresseme naturals then I loaded my hair with GVPCB and put a ziplock bag over my hair and turn the shower up so it steams. I proceed with the rest of my shower. I also let the water hit the bag so the heat can open the hairs cuticles. When I was done I removed the bag and rinsed with cold water added a little bit of leave in and then sealed with oil on my ends. OMG did my hair completely feel and look so different after that I actually do this every time I shower now.
I did the leave in and oil before I tried a "quick" DT in the shower, it helped but not like this. HTH