I use Hoppes Bench Rest and a good qualitywirebristle bore brush.Thebarrel of my .300 Win Mag got very fouled several years ago. This gunhasa28 inch barrel that is hard to clean because of it's length.
It took aboutfour or five cleaning sessions with the bristle brush to do the job. I pull the solvent soaked brushin and out of the barrelabout 20-50 times and then let the gunlie on the cleaning pad for about 30 minutes and then run patches through it.Do not use those spiral looking brushes that are made of stainless steel.

Some folks say that Hoppes should not be left in a gun with a stainless barrel.