How to get Russian troops to surrender in large numbers

Instead of using drones to kill them one or two at a time, drop leaflets and broadcast a message from a loudspeaker on the drone.

What matters is the method that gets the most Russian troops, alive or not, to mass surrender. 

During Desert Storm, Iraqi troops surrendered to drones by waving white flags when the heard the drones' engines. 

Iraqis Surrender Gulf War Operation Desert Storm 1991

It's unlikely Russian troops will retreat Highway of Death style, and Ukraine does not have enough combat aircraft to intercept a retreating convoy.

Highway of Death; Desert Storm/Gulf War