To get past the second set of turrets to find Classi in The Thin White Line in South Park: The Fractured But Whole open the time controls and pause time to drag the propane tank in front of the fractured wall:
Use Snap N Pops to ignite the propane and stand next to the propane tank and cause an explosion:
Go into the wall and hover over the windmill and select the kite icon:
Go to the highlighted area and follow the button prompts. Exit the wall and use Snap N Pops to pop open the wire box:
Enter investigation mode and hover over the wire box. Select the hamster icon, go to the highlighted area and follow the button prompts. Go back into the vent and talk to your buddy to get back down.