I just used plain polyester sewing thread and my zigzag stitch. I didn't concentrate on getting it really thick on the first time around and just went over the letter twice. The second time over filled it in nicely. I was not kidding when I said 5 minutes, that is really all it took to do the letters. I did mark the fabric with my Frixion pen for getting my letters straight and then just ironed away the lines.