One of the things that has, in my opinion, slowed the adoption of tubeless tire technology in road bicycles has been the "hassle factor" of dealing with punctures that can't be effectively sealed while riding. The sealant inside the tires can typically do a great job of handling small punctures, such as those from "goat heads" or wires from radial car tires, but it's been my experience that for most punctures or cuts that are larger than ~1mm, the sealant just can't do the job without intervention. This is most likely due to the higher pressures and lower tire air volume in this application, as compared to other bicycle types such as MTBs, where tubeless technology is the default at present.
When I first started sampling road tubeless technology, the "intervention" mentioned above meant putting a spare inner tube inside the tire, with all of the mess (sealant) and hassle (tight tire beads) that entails. In fact, I was pretty discouraged in my first forays into running a tubeless road bike tire after 2 out of the first 3 rides on one resulted in cuts too big to seal and a struggle to install a tube. I really didn't "get it", especially when the performance/reliability of regular tires with tubes (latex, of course) inside them was quite good for me.
Anyway, sometime after that "experiment" with road tubeless, and about the time I started thinking about putting together an "all-road" bike, I came across this internet thread:
In it, you'll see a discussion of a technique that some mountain-bikers had adopted of carrying along small swatches of cotton cut from old t-shirts to use as a plug of sorts for large punctures and cuts which tubeless sealant couldn't solve alone. The technique involved carrying along a short piece of wheel spoke to "poke" the cotton swatch into the hole to allow the sealant to have something to congeal on. At one point in the thread, someone mentions using cotton string...and that got me thinking.
I had seen a small tire plug kit that is produced by Genuine Innovations that consists of a miniaturized version of a tire plug tool used for automotive/motorcycle use. This plug tool basically looks like a screwdriver handle and shaft, with the tip being a small, 2 prong fork. The idea is that when a puncture happens, you load the fork with one of the "strips of bacon" (short lengths of cord covered with a somewhat sticky rubber substance). You then insert the tool into the hole in the tire, give the tool a 90-180 degree twist (so that a small loop is formed inside the tire) and then pulled straight out. Knowing all of this...and then seeing the use of cotton with tire sealant, I began to wonder if simple lengths of cotton butcher's cord (like used for tying up roasts and the like for cooking) would work?
Well...it turns out it works, and quite well! In fact, this is now my first line of defense in dealing with a tubeless tire puncture that won't self-seal. I save the supplied "strips of bacon" for cases where either the sealant is dried out, or the conditions are too wet for the plain cotton thread to work.