Same here!
I use a plastic coffee can with warm water and dishwashing soap.
This method makes it an easy job for hooked breech guns.
Now my flinters with pinned barrels, I use a device that looks like a c-clamp with a hose and o-ring that fits over the touch hole.
I'd stay away from petroleum based oils in the barrel unless you clean all the oil out, as it will foul powder.
It's also not a bad idea to remove the lock while you clean. Lots of crud works its way behind the lock.
