I've been considering buying a hand-held steamer and adapting a hollow tube to reach all the way up into the breech area. Then just plug the vent, decline the barrel and use hot steam to wash and rinse out the powder residue. While the barrel is still heated from the steam, run dry patches up to absorb any water, then let it dry. Then, lube with Ballistol, and be done.
I did remove the barrel this past weekend, mainly because I wanted to get powder residue off the underside of the barrel, which seems to attract moisture and hence, rust. I did not flush with hot water, but rather, just soaked with Ballistol, used a scraper and some patches, and the patches started coming out clean fairly quickly. I do think just removing the lock may be sufficient, though, wiping the barrel under the vent, and giving a shot of Ballistol before putting the lock back on.