I have had universal success with LMF on GM barrels. I draw file, then blend with maroon scotchbrite. The bore is plugged. A hanger is devised. I degrease with whatever is handy. Carb cleaner, acetone, degreaser for painting cars, dish soap, just do a good job. Wear disposable gloves. Work on clean newspaper. Set the barrel up on something on the bore plug. As previously stated one pass with a damp, and only damp, applicator. If there is enough to run, that is to much. It does not hurt to warm the barrel in cold weather to hasten evaporation. About 100* is enough. Then hang it up for 12-24 hours. I hang it in the shop. No heat, no sweat box. The humidity in my area is low. Temps are normally 50 to 70*. In 12 to 24 hours I have rust. Card carefully. Do not scrub it. My best carding thing is a natural brissel brush 6" wheel run at slow speed on an ancient motor. Some use cloth to card. Don't get after it with steel wool or a coarse wire brush. A real carding wheel is great if you want to buy one.