I'm getting braids this weekend. I ALWAYS wash my synthetic hair prior to braiding. When I do this I don't get the outta control itching and I think it keeps the synthetic hair from "cutting or tearing" my hair.
First, I wash the synthetic hair with diluted clarifying shampoo. I rinse the shampoo out. I then do a acv rinse. I do one final rinse to get rid of the vinegar smell and I hang to dry.
I have always had success with my braids using this method.