Q1: The majority you should be able to just inject more CO2 and keep going. After you get a good initial seal. But I wouldn't say "all except severe." There are some tricky punctures that don't seem that big, but have trouble sealing for whatever reason.

Q2: Absolutely not - you should not expect to replace a tubeless tire except for cuts nearly as bad as would make you replace a tubed tire. If a plug attempt fails (back to that in minute), you can always just patch the tire from the inside using a regular patch kit. You can do this on anything except severe cuts. It's annoying because you have to clean out all the sealant to get access to the interior of the tire. But it's usually preferable to just throwing out a tire. Actually whenever I'm doing a 100% sealant refresh, I'll go ahead and pull out all the old plugs and replace them with patches, just because patches are drop-dead reliable.


The plug. Plugs and sealant are a system that work together. The plug just helps the sealant do its thing. So after you get the plug lodged in there well you want to rotate the tire down so the sealant pools up right over the plug, and then add air gently. Once it seems to get an initial hold, spin the tire around a bit. Then add more air. Repeat until you're confident it's a good seal.

Also remember to "double up" the bacon when inserting (I've seen a few people get this wrong). Like the image below.