I use Dawn and Lemishine. Although I have not tested and observed enough to give a precise formula (I'm lazy), my impression is that less works better. Too much Lemishine seems to dull the exterior, as does leaving it running too long, maybe due to acidity? A large pinch, a short 1/4 teaspoon, seems about right. Also need to rinse thoroughly. When I get it right the brass shines like new.
Paul