I was trying to add some pics but keep getting error file too big message. Anyway I have been having great success making right and left hand ropes 3 strand thru as many as you want strands using 'single strand flat waxed nylon' fly tying thread. It's called Ultra Thread by UTC made in the USA. It comes in 70, 140,210 denier sizes and I get it at Sportsman's Warehouse locally. The 70 denier 6 strand, left hand lay is about .025" and is limp and heavy enough to hang in smooth looking curves.
This thread comes off the spool with no discernible twist, it looks a lot like dental floss.