Another thing to try is to work on the kinks by whipping the cord up and down while un-twisting it. I have a long cord that has that problem. I'll take it out in the front yard and whip the cord up and down while turning my arm opposite of the twist in the cord. Then I'll pull the cord in and repeat the process. It sometimes takes a couple of passes but it really seems to work well. And doing it on a hot day does make it easier.
Good luck,
Tony