Perhaps I shouldn't be answering in this forum, because I'm not a gun writer. I don't even pretend to be one. However, I've cleaned lots of muzzle loaders.
I don't bother with boiling water, although it has the advantage of drying faster than cold water. Glass cleaner with ammonia, mixed with an equal volume of water works well.
After taking the barrel out of the stock, I put the breech end of the barrel in a plastic container with the cleaning mixture. I then put a wet, snug fitting bore mop on a cleaning rod and run it up and down the bore. It will pull cleaning solution into the bore through the flash hole, ensuring that the flash hole is clear and clean. After that, a quick wipe down, dry and lube and you're done. It only takes a couple of minutes.
