With solid precious metals, you still need to use a great deal of care. New jewelry is one thing to work with. A worn piece may have several thin areas and can be seriously damaged. A well worn ring band can develop sharp edges in a matter of seconds. This can be severe enough you will need to put a new shank on the customers ring.
Worn prongs are another problem area.
You can quickly remove enough metal that they will need replacing. So always inspect the jewel carefully before polishing, then use great care not to remove any unnecessary metal. Look for any area that is thin and weak. If the customer's ring has deep scratches but a thin band, don't use a bobbing compound on it. Just polish it with rouge and explain to the customer that you cannot get a satisfactory finish at this time.