i very rarely polish past 220 grit - often 180 is perfect....on a longrifle bbl, that is. i remove the tang and screw in a brass rod threaded for the breech, and drive a hardwood dowel into the muzzle. the to the laundry sink and scrub with Comet - not Old Dutch - and a scotch brite pad. you cannot overdo this. in sight slots and around engraving and bbl loops, i use a stiff toothbrush - my wife's. i don't like the taste of comet myself. never touch the bbl again with the fingers. i use two cotton batting balls, bought at the drug store, dipped into a shot glass full of solution, then squeezed out, to apply the liquid full length in one slow stroke. i like a q-tip for sight slots. the bbl goes into the damp box suspended by a screw eye and a hook. i record the time in and out and muzzle up or down, reversing at each application.
to card between coats, i have a four inch long roll of cotton canvas about two inches in diameter, and i scrub the barrel hard. the barrel, for solution application and carding, rests horizontally on its end plugs, on two wooden v supports.
five or six applications, two - three hours apart, yields a good, rich, dark brown, that is matt but very smooth. i kill it in the laundry tub again, with super saturated baking soda and a finger nail brush. then i pour a whole kettle full of boiling water over the barrel, held vertically. while still hot, i dry with clean paper towels, then apply motor oil. the steel loves this part.
now, even after all of that, i occasionally find a small spot where the steel is not perfect. but it is rare. i usually shrug it off.
laurel mt forge is the most difficult to use, but it gives a very solid and deep brown.
