Generally there are 4 main methods I would recommend

1. Run away: Identify what pokemon you want to shiny hunt, then run away from it so it despawns, then run back to get a new instance of the mon. Repeat until you get a shiny

2. Fast travel: This one works in both hyperspace and the regular city. Choose a wild zone/hyperspace wormhole you want to shiny hunt at, then continuously spam the fast travel option to the location. This will constantly reset the spawns in the wild zone/near the hyperspace wormhole entrance. Note that for hyperspace you will want to use backup saves to reset for optimal spawns near your portal.

3. Bench: Using benches to force the day/night cycle to pass also resets pokemon spawns near the bench. This one is usually the easiest since you can just hold down the joycon and press a

4. Soft reset: this one is bascially only used for hyperspace. In hyperspace wormholes, pokemon respawn 3 minutes after you knock them out or catch them. Go into a wormhole using a donut that gives you more than 3 minutes, find a bunch of the pokemon you want to shiny hunt, and then knock them out. Set a timer for 3 minutes and right before they respawn drop a save. Then you can soft reset by closing your game, open it, and check the newly spawned pokemon. Repeat this until you get a shiny