What program are you using?
I use gimp, all i do is add an alpha channel to the layer and select the stuff i want to cut out (usually with magic select) and then hitting delete.
Then sometimes i use the eraser to clean up stuff.>>6418844
i see you must've figured it out.
Yeah that one's pretty hard to do that with since the lines sorta fade out and it's hard to figure out what should be a part of the art or not.
as you can see so