I like to wash the hair with Timotei, condition (don't take the conditioner out!) and after conditioner has been sitting in the hair for 5 mins+ boil up some water in a pan and dip in the ponies hair.
I then pull out my pony and comb her hair out flat, followed by styling. And just so you know, curls are suuuper forgiving!
My method should kill those braids, and for tail rust I remove the tail and bathe it in oxy solution.