*My way* I finished the games main story, got fully modded up, then went for this trophy. You can select invasion via your in game mobile phone, multiplayer. If youre in a rush, go straight for the activation and hope the other guy doesnt see you. Id suggest to quickly scope your area, get a good hiding spot, and go for it. This can take forever to reach 100%, be patient and dont move, even if the other guy is approaching, he might just pass you. All the best.