Tips for dealing with damage from a Brazilian Blowout?

So I'm starting another natural hair journey after 8 years :') I went natural in 2016 after a big chop, and my hair was at its peak in health/length in 2022 but I was getting exhausted with all the upkeep. I did a relaxer and then a year later decided I'd start transitioning again. Fast forward to a week ago, I was 12 months post relaxer and got curious about Brazilian Blowout (keratin treatment) to help me deal with the new growth texture. Little did I know it would make my hair start falling out with intense shedding my first wash day post treatment. Its so thin now and I'm so afraid to touch it, its very fragile especially when wet.

Has anyone delt with this? My first priority is - how do I get this stuff out of my hair?? My plan is to wash once a week because its a temporary treatment thats supposed to "wash out in 12 washes". Other than that I'd love any other ideas from this community <3