I make a lot of sterling chain & the approach I use is basically
the same as Tim's.
Heat the entire piece, place it into a warm/hot pickle bath
while it is still hot. Let the pickle do its' job until the piece
has a milky appearence. Tumble it for about 1/2 hour in assorted
shapes of steel shot with a pinch of burnishing soap & about 1 oz
of household ammonia.
Remove from the tumbler & repeat the heating, pickling, tumbling
routine a minimum of 3 times, more is better. Most everyone that
sees stuff done this way comments on the polish. It tends to stay
bright considerably longer than untreated sterling.
Using fine silver (.999) as opposed to sterling (.925) is
another way to reduce the tarnishing significantly. That's
basically what you'e doing by the heating, pickling, tumbling.
You're raising the silver content by disolving the copper with