Tumbling is a pretty low impact way to polish. If they are badly tarnished, you have two choices, use stronger chemicals (bad idea) or use a more aggressive cleaning method. I have read of people chucking them up in a drill to polish, or get some stainless steel pins and a rotary tumbler..... Of course, a new tumbler is a big investment just to make them pretty.... If you have a treadmill, I read about someone getting some SS pins and then using a regular old Gatorade bottle on a treadmill (Gatorade bottles are not smooth, so that quickens the process) Set it on a treadmill and let it roll (you will have to fashion something up to keep it from rolling off....)
Or , if you are not opposed to spending a reasonable amount of money, harbor freight has a rock tumbler for $40 that can be used with stainless pins
http://www.harborfreight.com/3-lb-ro...ler-67631.html