The flex hones referenced in this interesting discussion of honing barrels (and UK proof of same) in my experience are practical useless as a "hone"-- they do a fairly good job at polishing. Honing shotgun barrels requires a substantial hone such as those made by Sunnen. There is also a firm in Tennessee who makes a hone.
The late renown gunsmith, Jim Kelly of Darlington, SC had his photograph using his hone in an article about him in the South Carolina Wildlife magazine and that article was added to a post on this BBS. I attach that post it here for those of you who are unfamiliar with honing machines.
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=617032&page=2Kindest Regards;
Stephen Howell