Run a patch through with windex or alcohol on it
Then run a dry patch through until it's crazy shiny inside
Never use silicone oil in the barrel because, as stated above, lubricants trap dust and actually make the barrel dirtier faster. The BB isnt riding the walls, so lubrication isn't going to help anything.
BBs dont ride the top of the barrel. They just don't. The magnus effect doesn't work inside the barrel due to air pressure, and even if by some other principle the BBs were riding the top, you'd see a clear line across the top in a dirty barrel, and that's just not the case.