Air Gunner/Radio Operator Badge for Luft Ground Crew?

[pzgren1944]

Hello;
this is my first post and I'll start with a question I hope someone be able to help me with.I have read that the criteria for Luftwaffe ground crew being awarded the air gunner/radio operator badge was two month's time in service after graduating from the technical school.I've also read that until the badge was awarded,personnel wore the cloth "trade insignia" on their left forearm sleeve.Is this correct as to the time involved or was it longer?
Also,if a ground mechanic was awarded a badge then later was transferred into a flight engineer position,would he then be sent to the flight engineer school for the full course or would they get an abbreviated course and awarded a second badge?
Thanks for letting me be long winded!