The words "must use 100% cotton thread" are words I have difficulty with. Poly/cotton works just as well. Foir years I quilted with regular sewing thread in order to get colors I needed. I will use a thread saver such as "Thread Haven" to keep from tangling. I have started using the finger tip stuff like Tacky Fingers which seems to be working better in preventing tangling. While cotton is preferred there is no "law" that says you must use it. There is always a reason certaing things are preferred.