Learned this trick a few weeks ago and tested it out and it works amazing. If you get a flat on a tubeless tire and the sealant won't hold it, just stuff a piece of t-shirt (socks, underwear or even some shop towel worked for me) into the hole with a 2mm allen key and hit it with the CO2 and you're good to go.
I fixed a friend's tire with this technique with some shop towel and it was holding 3 days later after shuttle laps in Revy and on Mt 7. It was a largish hole in the sidewall that nobody thought would hold. And since you usually catch a tubeless flat before it's totally empty, you only need one CO2 to get it up to pressure.
Makes packless riding easier when all you need is a piece of material, a CO2 canister and dispenser and an allen key set. Put a chain link inside the end of your handlebar with some duct tape too for good measure.
On my DH bike, I put 2 CO2 canisters and some material inside the seatpost.
I'm going to experiment with the Lezyne CO2 hose so that I always have a dispenser on hand. They will fit inside a handlebar, except for the end. Would require either trimming the bar 10mm on one side, or sliding your lock on grip out 10mm on both sides.
I also have been running a money belt that I tuck into my shorts on the front when I ride my DH bike. Mini tool, CO2 dispenser and phone goes in there. Don't even notice its there when I'm riding. Keeps tools out of harms way when you crash so you don't end up with a huge haematoma in your leg like I did once.