On my T/C Hawkins Flintlock.. I pull the barrel from the stock first and foremost. I also pull the vent liner every time I clean the rifle. This of course makes for a larger hole. After the VERY hot soap and water bath with lots of hard fast pumping action, I put a bore brush on the ramrod and wrap a patch around that. I saturate that witha good black powder solvent. I then brush the barrel only about five strokes. This is to make sure nothing is building in the rifling.

After that I use either brake cleaner or alcohol and spray down the barrel and through the vent liner. I then patch all of that out of the barrel. After that a few dry patches to make sure there is no moisture in the barrel. After that I take a fuzzy pipe cleaner and clean out the vent liner hole. You can reach all the way into the breech of the barrel with this.

And then I put some Birchwood Casey Sheath on a patch (saturated)and swab the entire barrel. After that I clean the lock on both sides, as I remove that also. I then spray a light coat of silicon spray on the back side of the lock, and wipe that all off. After replacing the lock and wiping the under belly of the barrel with the Birchwood Casey Sheath, I reassemble the rifle and wipe all the parts I did not get so far, with the Sheath.

I have never had a problem with rust, ignition problems from the Sheath, or any thing.. so far. I do swab the barrel out with alcohol before loading, and wipe the frizzen, pan and flint off though also...

I agree with you and you idea of not wanting too much bore butter in that area, but to each their own. Lots of folks use it and have no problems with it....