As some else said the only way you'll be able to share your ticket is by sharing your phone as mobile passes can only be downloaded to one device.
I don't have an Apple device so I can't speak for that but I know for certain that screenshots will not work on android devices as a new code generates every so often specifically to prevent sharing.
On Sunday I saw people who were having trouble scanning Print@Home tickets being asked for ID to match the ST holder name on the ticket. I don't believe the club will allow Print@Home tickets for the flexigolds, I think they've designed them with preventing reselling in mind.
Quite simply, City don't want to make ticket sharing simple to cut down on touting. Flexigold works for them as if ST holder can't attend then it will go onto the exchange at a matchday rate.