I've tried various things hate using vinyl electrical tape for these for the same reasons Rick stated. I've never had much success with the liquid tape for some reason. but the tool handle dip rubber coating seams to work. My cords usually don't just get nicked though so I wind up either having to make a full splice repair or if the break is near the end I wind up cutting it and end up with a shorter cord with a replaceable end once that is done if there are any new nicks I like to remove the end and use heat shrink tubing.
3M also makes a heat shrink tape that you can simply wrap around then heat it to allow it to vulcanize itself.
If you can't find the go2 glue you might try shoe goo That TV advertised flex glue may work with the sheathing like Rick has done. One nice thing about his repair is it is not very noticeable unlike most other repairs.