As far as needing to use snap caps to prevent damage in a Glock, they are not needed. The design of the gun and parts doesn't make the weapon susceptible to damage from dry firing. I think the OP was talking about using them in place of live ammo or an empty chamber.
I treat dry fire practice like malfunction drill practice in that I pulled the trigger, gun went click, I tap, rack reassess.
Dry firing is necessary in all firearms to building trigger finger strength, muscle memory and develop proper trigger control.
I'm game though....
Former Certified Super Glock fixer