The only thing the cord needs to be is 1. Strong enough not to break, and 2. thick enough so that when you wrap it around your hand to pull in tight spots it doesn't cut your hand in half. Leather gloves are your friend. Do little circles in the corners to get the gasket seated.
Also the thinner it is, the more likely it will be to tear the rubber if you pull it wrong. 3/16-1/4" rope is a good balance, and I will try that wet trick next time. Genius!
HB olfa knife blade flat against the glass to remove outer rubber flange works every time to remove the old gasket and get the glass out. Never broken one. Old gaskets can be rock hard, so it takes a bit of pressure and repeated passes, so wear leather gloves and eye protection for when the blade breaks.
Got lots of tricks for putting it in, just a bit hard to explain. Most important is to get the gasket on the glass 100% all around before you put it in on the car, so that it sits down into the window opening as far as possible all around before you start roping yanking. It should look like it's almost all the way in and down all around. If you can't get it seated well to start with, it will rise maddeningly at the top especially and make it impossible to get the gasket on the pinch weld. If you do it right, your helper really only needs to keep the top center held down as you do the rope thing around the bottom and sides.
Last trick is using a flat plastic tool to help you seat the gasket all the way over the pinch weld as you go along. This one is my favorite.
When you push it between the glass and gasket (inside, 90 deg to the gasket)) and pull toward you , it forces the "U" of the gasket fully over the pinch weld. If you're not over the pinch weld fully at the bottom, the glass gets offset toward the top too much, making the top very hard to get it started and seated up there. Once you get to the top, using the tool also helps you get the gasket over the pinch weld and finally all seated in place.
Anyway, hope this helps. The first couple I did were a bear, now I can do it myself if I get in and out of the car about 1000 times to whack the glass as I go along to keep the top in place. A big sand bag is also handy to help hold the top center down and in place if you're alone.