Since wonder guard can't be transferred using role play, skill swap, power of alchemy, or receiver, the only ways to transfer it are entrainment and trace. If you want to use entrainment, then you need to have an ally use entrainment and have Shedinja mimic it, and then have Shedinja use entrainment. If you want to use trace, then you need to switch in a trace Pokemon when the opponent's active Pokemon is Shedinja. The first takes three moves to set up, so the opponent can pretty easily defeat one of your Pokemon during that time. The second is unreliable, as most opponents won't have Shedinja. So there are ways to transfer wonder guard, but there are no good ways to transfer wonder guard.