How do you get the guy to move to get to sunnyshore city?

If you mean the guy blocking you because of the blackout, just follow the storyline. You do NOT need any special Pokémon or pass or ticket or whatever to get inside.

If you’re asking about Flint blocking the gym, you’ll have to go to the lighthouse on the southeast side of Sunnyshore first, then talk to Volkner. He’ll go back to his gym and you can enter.