I also struggled with making the wire “straight.” Even a slight wavering of the wire when finished and placed was frustrating. I tried multiple methods to straighten the wire, but it’s just a fickle material. Its main benefit is flexibility, for sure, but if I’m laying into non-moving parts, I want it to be as smooth as possible. EL tape is a better option, but not as cheap. By the next time I make a costume, I’ll have some form of LED wiring experience and learn to diffuse it properly enough to create smooth continuous light. (Hopefully.)