I'm sorry this happened to you. I made the mistake of not detangling braids after a weave take down.
You actually are to detangle braids BEFORE washing. Otherwise, the shed hair from a month & a half will cause major tangles.
What I did today, after having flat twists in for a week, is put conditioner on my dry hair. You can try that and detangle before washing. That will get rid of the shed hair and cut down on the tangles when you wash.
I agree with Reg's Wife that you should detangle before you wet your hair. Now while I wear braids for a long time, I redo them one by one frequently so I'm constantly removing shed hair. And when I undo, I undo with fingers
moving down the braid slowly and detangling as I undo. I imagine leaving the braids in for a spell causes there to be some knotting at the base, which is where your patience is called to play and you have to be very gentle. Now one thing that will help you relax is to remember that your hair was braided with strands being parallel, and held in place so that it wasn't free to wrap around itself the way it might if you wore your hair in an afro. That should give you the encouragement and peace of knowing that detangling is really just pulling strands apart. So when you get to the base where the hair might be stuck together, use the technique of moving the section back and forth till the strands start to separate then use your fingers to pull them apart. Also once you have separated the strands of a few braids, I'd braid them together making sure to keep the strands stretched by smoothing as you braid. That keeps the strands from wrapping around each other while you work on the rest of the hair.
I am not a fan of washing hair unless it is braided so I'd even recommend getting your hair wet when in the big plaits. Then slathering on conditioner and undoing each big braid and combing through starting from the tips and working your way down. Don't freak out about shed hair coz each day's 100 shed hairs were trapped in the braids. Once you comb through, braid the detangled hair again. In other words, you should not leave you hair to shrink up on itself when wet or it'll be a nightmare to comb.
And from now on, only ever wash your hair when in braids. You can do many small braids that you don't undo until you hair is dry. Or you can do big braids that you undo and comb during the wash rebraiding each section before moving to the next. And so on.
I don't know how you twist your hair but if you could learn to twist so that each strand gets twisted in the same direction before being wound around the other in the opposite direction as someone very clearly explained better than my
lousy vid shows, you will find you can wash your hair all the time in twists and never have to deal with detangling. As you can see, twisting my hair that way keeps the strands parallel to each other so that undoing is just a matter of
twisting the opposite way and then separating the strands. I do this only to redo my twists. Otherwise my hair is never wet unless it's safe in twists.
I hope you'll find out which methods works for you and that you will realize that detangling doesn't have to be a nightmare or take half a day.
Hugs,
ETA I like Pinkskates idea of letting hair marinate. When you put it in those plaits I recommended after undoing braids, maybe slather on conditioner before the plaiting and baggy your whole head for the night so that in the AM it will just be slip city when you try to run a comb through it!