I always squirt through the valve when topping off, it's just easier when there are a million other things in life competing for my time.
However, I do always wind up with clogged valves and running an Allen key etc. through them doesn't seem to fix it. So, when that happens the tire comes off. This is with Stans btw.
I used this for my first foray into tubeless circa 2010. I liked it, never had an issue sealing but then again I've never put a ton of miles on a MTB. When I used it all up I switched to Stans for convenience since that's what's always available locally.