Unfortunately, this horse has been beaten 'til its ears bleed on more than one occasion. What we all need to remember is that there are people reading this forum for information and not arguements. Allow me to make some observations without endorsing or condemning any method.
I too had serious reservations about cleaning with water when I started, those reservations were quickly dispelled once I got the bugs worked out. Real Black Powder residue is "hygroscopic" (it will attract moisture). Therefore it does make sense to use at least something that replicates water to clean it. In my experience (which is not vast), solvents, be it BP or Smokeless do a less than decent job of cleaning a BP gun. Hoppes No. 9 in particular is something I would not ever us again, that's too much work. Conversely, using what I use to clean a BP gun doesn't work for smokeless guns, I learned that the hard way.
I tried the dishwasher trick last year at my daughters house,(my dishwasher at home is a redhead and she refuses to clean guns unless she shoots them) it was easier to clean them by hand. That and I got flash rust after leaving them in the dishwasher through the drying cycle, oops.
I've also tried the oven method, same result, flash rust. Not only that, it was hard to clean the rust off wearing oven mitts. Note to self: Oven may have been just right for muffins but not a Dragoon.
The bottom line is, experiment and find something that works for you. Once you've found your pet method, share it with us. I promise that none of us will use all of it, but even the most stuborn of us might just "Borrow" part of it.
WD-40: Use it if it works for you, personally I don't care for it for much of anything.
Hot Water: Love it or hate it. If you hate it, let those who use it do what works for them. It works well for me.
Oven: Refer to Hot Water with the exception of the Oven part.
Ballistol: Originally formulated for BP cartridge guns, it does work if you can learn to like the smell.
The only thing that matters is Clean thoroughly and clean well. If you miss a spot you will sooner or later find corrosion there.