I've seen this trick on Pinterest--posts claiming that you can untangle doll hair with fabric softener.
Just mix fabric softener with water, spray it in, and comb it right through.
It made sense, but it seemed a little too easy.
Successful, but not that easy.
This doll's hair was really, really tangled in the back, and the spray worked great for the little knots.
The big ones were just too much for it.
In the end I just wound up dipping the whole head in fabric softener, which worked much better.
The process, combined with the splatter from combing, was not pretty.
It took around 15 minutes.
It did leave a little greasiness behind, as I didn't rinse it out super-well, but it's been easier to brush out since. The remaining bottle of doll hair detangler spray will do the job from now on.
Totally worthwhile for a favorite toy, but I will not be redoing the rest of the dolls this way!