By using a single-base powder and plastic wads there are a ton of recipes out there in 12 gauge under 6,000 psi chamber pressure to use in your Damascus barreled shotgun.
You don't have to go the fiber wad route if you don't want to but if you do there are a ton of them out there. All black powder shops have them and Circle Fly, Track of the Wolf, Dixie Gun Works all have web-sites that you can mail order them.