basically the same thing
it depends on the severity of the swirls. you can post a picture to let others get a better idea of what direction to steer you in but most of the time you'll need to start with SHR.
every car and paint finish type are different, and factoring in the condition of the finish, it can take anywhere from a few hours to a few days to correct an entire car. I spent about 6 hours on my Corvette just correcting the paint, and in comparison to most cars C4's are small
It will be better for both you and the car for paint correction to be done in the shade. I would ask a friend if you can use their garage for a day. You don't want the surface of the car to be hot when you do this, and you don't want to sweat to death either