I'm working on a Halloween costume of taffeta, and it's my first time working with this fabric. Because it's just a costume, it's an inexpensive polyester taffeta, but obviously I still want it to look good. I just started sewing the actual taffeta pieces today, and all my seams make little striations, like thread runs, in the fabric. I read on one page online that a ballpoint needle may solve this problem, but the ballpoint seams look the same as the fine, sharp needle seams. They are most noticable in the seam allowance, and maybe with some gentle rubbing and pressing, they won't be too noticable in the finished piece. But does anyone have any other suggestions or tips that I can try?