I discovered a neat, little trick for gathering tulle the other day. It starts with zig-zagging over dental floss. I positioned the dental floss in the loop of my narrow-hemming foot to keep it centred as I was sewing. I used a fairly wide zig-zag, so as not to get the dental floss caught. Then, because I knew I was short of dental floss, I kept the floss under tension. This had the added bonus of gathering the tulle evenly as I went, saving the tedious hand gathering step. You can see it gathering behind the foot in the photo above. Pull the floss tighter to increase the gathering. The amount of gathering can still be adjusted after you have finished, as long as you have not cut the floss off too short.