I have a long wig like this. Here's how to do it, the poor person way.
Fill the sink up with waer and wash the wig in it. You don't need shampoo, just condition it. Or use detangling spray. With some conditioner/water in it still, hang it and brush it from bottom-up wih a normal hairbrush to get out normal tamgles. Comb it with a wet comb that's laced with conditioner. DON'T LET THE WIG DRY WHEN IT'S BEING BRUSHED. Wrap it in a towel to dry. It's fine to have some conditioner in a wig.
Whe you aren't usuing it, put ponytails at the bottom where the hair ends. If the bottoms can't move, the wig can't tangle.
Something else that I've heard is that once you have it styled is that you should hairspray it into place. This might be common sense or sound absolutly stupid; I'm not sure. That's just what I heard but it might be worth looking into ^^'