Annibee is right, definitely go and buy an epiccosplay wig! They are the only ones I wear for long haired cosplays now since they are so much easier to untangle. I don't even need wig conditioner on them before I brush them out after wearing.
I use a flat metal bristled brush meant for cleaning wigs, I find it has less static than plastic. Never use a round brush on long wigs, they'll get stuck.
I love cosplaying long haired characters the most and they do take practice, you have to be aware that you're not getting tangled up or sitting on it. But the better quality wigs make all the difference in how good it looks and how easy it is to care for. I used to use newlook brand wigs made of a pretreated/coated kankelon, they were the easiest ones to keep tangle free. And I still had to cut them into layered styles and keep them in a ponytail with a ribbon when I was just walking around a con and always stay out of the wind. It would take me up to three hours after wearing a knee length wig to untangle it.
I am upgrading everything I possibly can to epiccosplay wigs now!! It literally takes me ten minutes to untangle!! It means I get to sleep after i cosplay instead of trying to untangle wigs before I put them away. ^^