I browned a rifle I build almost 30 yards ago. It was a solution that came in a bottle. You had to steel wool the barrel, wipe it off with denatured alcohol, then smear this stuff on. Wait a while and it starts to rust the barrel brown. I had to do a lot of coats to get the color I wanted. I was looking at the rifle the other day and it needs to be re-done as the barrel is almost back to the White. Too many times cleaning I guess.

Birchwood Casey makes a Browning solution and I think Brownells makes one as well... you could look there also.