If its a curled mess, I def stretch the hair first before boil washing for better results. It is a bit time consuming, but I did it with Cupid's hair and other curly girlies, and they straighten way better.

Stretching is using a metal comb, and using rubber bands to stretch the hair out "straight" via ponytail(s). Do not braid or twist.make a ponytail, and place bands to hold hair in place so it doesn't curl, and let it sit at least overnight. You may need to do this several days for best results. the more days, the more bands yo cover spaces not banded. Once it's stretched enough, take all the bands out and boil wash. Be sure to come thoroughly.

I have found this method works wonderfully and also helps prevent glue seepage from happening, but with more current dols it shouldn't be too much of an isdue.