How to re-suspend silver from the dried out silver paste?
According to SPI Supplies:


  If the Dotite Silver Paint dries out, unlike some other silver paints, it can be re-suspended with the addition of SPI #05004 Silver Paint Thinner followed by an ultrasonic bath treatment.


Generally, ketones are used as diluents, also for conductive paints (acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK)).