I roll the end between my fingers and it goes through no bother (ish!). They work great, for bigger holes you can pull the loop back through to make a W shape instead of a V, and then cut it. Don’t work so well if they’re v. near the bead.
Yeah you can patch the inside, infact if you’ve got a bigger rip then I think that the string is best removed and a proper patch put on when you get a chance. I just clean the inside of the tyre, rough up a lot and put in on there. Sometimes it sticks fine once I’ve had a problem and superglued a bit of inner tube over the hole, worked great.