With shotguns, muffs do not work for me. The mount knocks them off. I do use them over plugs with handguns,rifles and muzzleloaders.
I use custom silicon plugs. A two part silicon compound is mixed and poured into the ear where it hardens. db reduction is about as good as it gets, near 30 db.
The cheap disposable foam plugs are nearly as good, 27-28 db. They expand to fill the ear canal without a void, and work well with kids.