I recommend this method as a last resort.
Use this if you don't know how to use the sharpie method or if sharpie markers are too expensive for you. You can also use this if you can't see any sharpie markers with the color you want/prefer.
I have some warnings for you guys. After using this method, the texture of the wig might change and you wouldn't want to destroy your babies(wigs), right?
I dyed my Serah Farron wig because I'm not satisfied with the color, it's too light for me.
So here's what you need:
~Wig stand
~basin or something close to it (a basin that your mother won't get angry at you for using it)
~acrylic paint (be careful in choosing)
~newspaper (It's going to be a messy job)
~comb
~wig to be dyed
Check first the color if it's alright for you
Put your preferred amount of acrylic paint in the basin and add water.
Mix until the texture becomes something like this. It kinda looks plastic-ish.
Test out the color first in some few hidden strands.
Use the comb to "paint" your wig. I guess nobody wants a 1 hued wig xD
See the color difference? :D
For the curly part of wigs, I suggest that you just put the wig in the basin w/ the acrylic paint or you could do it by hand.
Finished Product:
You can see the original color here:
http://kionezhialeron.blogspot.com/2012/07/ayanamisatoru-wig-review.html
Note:
This method is already known to some cosplayers~
That's all~Hope I helped