If you should use the boiling water rust process I described,plug the bore and chamber.
While I do not claim it is the best sealer,I mixed a mush of turpentine and beeswax and rubbed it in hot .Seems to have worked.
As I said,I work right over the boiling water,boil,swab,card,boil,swab,card,till its done.I can do one in an afternoon.
I have a .40 cal take off bbl made by Ron Snover and the finish on his bbl looks just like what I do.I use the Express Brown #2.
I would recomend this for the pro smith to experiment with.It looks right on old guns,it would work on doubles.It does not look like a make-do job.
It is not,however,a perfect match for modern scopes,etc.