@ tofu, It'd be a lot easier to help if you posted pics of the characters and maybe even your base wig. Hm... Attack it with scissors?
Okay... here it is, my wig that's gone from zero to hero! <3
Ewww! Say it ain't so! As you can see this is a curly, tangled up beast. Surely it's impossible to straighten...!
Ha ha, I don't have a wig head yet so Buddha's gonna have to do.
Before straightening my wig with my hair straightener I attempt to brush out some of the curls to make the job easier. Seen above, my weapon of choice.
Progress shot! Part of the straightened wig is isolated in a ponytail to the side while the rest is everywhere. Buddha wasn't working so I tried thumbtacking my wig to my Haruhi plushie... It was a bit difficult.
And so I straightened on for at least an hour! It's a bit tedious but a lot more involving and less of a hassle than the hot water method so it was good times.
The finished product?
Ta-da! Now I just need to style it and I'll have me a Nami wig! Yes I'm a bit tired in my pics but it's the fatigue of satisfaction. Straightening wigs takes a while but it gives you such an accomplished feeling.
Excuse me on the pic-heaviness! Hooray for my straightened wig <3