1.Line the bottom of the sink or a glass baking dish with a sheet of aluminum foil.
2.Fill the foil-lined container with steaming hot water.
3.Add salt (sodium chloride) and baking soda (sodium bicarbonate) to the water. Some recipes call for 2 tsp baking soda and 1 tsp salt, whereas others call for 2 tablespoons each of baking soda and salt. Personally, I wouldn't measure the amounts... just add a bit of each substance.
4.Drop the silver items into the container so that they are touching each other and resting on the foil. You will be able to watch the tarnish disappear.
5.Leave heavily tarnished items in the solution for as long as 5 minutes. Otherwise, remove the silver when it appears clean.
6.Rinse the silver with water and gentlydaub dry with a soft towel. Leave out between a couple of paper towels until it dries completly.
The tinsel may or may not dry properly as the core may shrink. This method is probably the easiest and most efficient way to get the job done as it does not require any rubbing which might distort the tinsel itself. No guarantee that the tinsel will be salvagable, but it is worth a shot. You might want to try maybe a foot or so as a test.
Good Luck!
George