Recently been through just this, had a big enough hole that it wouldn’t seal, got Weldtite kit out but realised it was too dark to see the hole properly (have good helmet light but wear contacts which don’t give good close vision) so I chucked a tube in which slow punctured but got me home.
Used the Weldtite kit the next day (glasses on and in the garage) and it worked a treat, next time I’d have more confidence with using it trailside. Also realised that my tyre had almost no liquid sealant left in it so wasn’t going to seal anything but a tiny hole! Added sealant and it’s now sealed nicely with the Weldtite anchovy staying in as a permanent fix.
Think I’ll carry some cotton wool and a slime tube in future as having this happen again locally isn’t too bad but on a big day in the mountains it might have been less fun!