Deicing Rod for Propellers
A rod soft enough to not be quickly destroyed by the propeller (or to damage the propeller) would likely be too soft to apply impacts forceful enough to shatter ice along the full length of the blades.
A &quot;baseball card&quot; big enough to handle the full length of the blades, and also soft enough, would likely be blown aft forcefully enough to not touch the prop at all.
Frame challenge:  so-called deicing boots accomplish the same, with no risk of damage and with proven reliability, by electrically heating the blades to melt the ice.