I stopped using high humidity as I get a much better, more even brown without it. I degrease with acetone, hang the parts in my shower and apply the cold brown. Any incidental moisture (shower taking) is the only moisture it gets. I used to close the door and fill the tub with hot water to get steam, but all I got was streaky browning. Now my barrels are a fantastic dark brown, with a very even color from tang to bore. I only card with a piece of pillow ticking as the 0000 steel wool would take off too much scale giving an uneven look. Apply even coats that are thin, as heavy coats "bite" unevenly and give blotchy, uneven color. My barrels usually take 2-3 days to finish browning, then neutralize with baking soda paste, rinse in hot water and apply deer tallow/bore butter/crisco/gun oil. I also like to apply a final coat to the metal with melted beeswax after letting the greased parts sit overnight.