Rich,
Congrats on getting your Huntsman and other barrels back. :grin:
For the breech plug cleanup.. many methods work, but I can share the method I use if of any help.
I place the breech plug on a shop cloth,after wiping off the excess grease on the threads, and spray it with Gun Scrubber....turn it over and spray the other side of the threads. Just take care to keep this spray solvent away from your eyes,stock finish,painted items,etc. as contains chlorinated solvents.
I wipe off and place into a jar of Rusty Duck Black Off to soak while cleaning the rest of the gun. ( hot soapy water or Windex would also work if unable to find the Rusty Duck for soaking)
I also use the same RDBO cleaner on a large patch over a breech brush to clean the threads inside the chamber.
Takes a little fussin and the hardest area to get clean are those deepest threads running up to the shoulder leading into the bore (old toothbrush is helpful here). Traps a lot of crud there and a small flashlight is helpful to check that area during the cleaning process. :roll:
Have fun!,.......Primer