Can't remember the name of the green stuff i happened to have in my last rear tyre before the puncture?
Reason i put it in was because i had a slow leak and knew it wasn't the valve.
The tyre wasn't too far away from changing, but still had good grip, and when i got a screw in it, it never deflated AT ALL.
Got me to the bike tyre shop no problem.
BUT, they don't tend to do a repair at all with all that gunk, they're simply not interested.
So it's great gear if your tyre is past half way, or you have a slow leak, but once you put it in if you have another issue, prepare to pay for a new tyre.