It's pretty tough to come up with a method that won't eventually damage or destory silver-plated items , when cleaning/polishing them , dreamerscove .
The method I think you're talking about (baking soda/salt/warm water & aluminum) creates an electro-chemical action that not only removes silver oxide (tarnish) , but actual silver as well , and deposits it upon the aluminum .
That process , just like using a paste-type polish , removes the silver that has been deposited/bonded with/to the usually less-attractve metals underneath it , esp if the item is immersed in the solution for extended amounts of time .
Eventually , the silver plating is just gone & the 'ugly-child' metal underneath it shows through , sometimes in areas where you'd rather not see it .
Ultrasonic cleaning gently removes the least amount of metal or oxides of the metal , but that means sending it out to be done , or buying an expensive (& possibly large) ultrasonic unit .
If your item is not an expensive/valuable/rare/fragile one , I guess you can use any method that will work for you .
If your item is not used for food purposes , you can consider coating it with a protectant (to slow the oxidizing process) after it's cleaned/polished to your satisfaction .
The environment where you display/store your item can quickly affect how quickly it tarnishes , too (such as tobbacco/candle/incense/cooking smokes) .
