HOT water and soap is great. My preference is Simple Green for cleaning. After everything is clean to my satisfaction, I run a mop with Ballisol inside the barrel and all over the entire gun. I don't like WD-40 or Bore Butter either. Bad experiences with both! I'll never use either one on a gun for long term storage again. I agree with Hawg in that you don't want a petroleum based product. I've had guns stored for YEARS coated with Ballistol and when I got them out, ran a dry patch down the barrel and they were perfectly clean.
Black Powder: Not because it is easy, but because it is hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win...