It's gonna be a short tutorial, hope it helps you.
1. Create a gun and change it to a grenade.
2. Make a trigger that activates when the game starts (timer with 0 delay set to execute the trigger)
3. Change amount of shots for the gun to 1
4. Change it to shoot bullets.
5. Change the slot to whatever you want.
6. Make it for characters only.
7. Set the power to 0.001
8. Set the speed to whatever you want.
9. Change the recoil to how fast you want the propeller to move.
Use the tool you just created to move in zero-gravity entertainment, shooting from behind.