That's how it was done. He used the 'cooler' trailer like a dolly.

I have a dolly for my bike & Pop up Camper. Keeps all the weight off the bike. Only Problem is you feel like a freight train and 50 cars rolling down the highway.
And you get a little more jerking when speeding up or slowing down. It was designed and built by a guy in a wheelchare I met at that last Austin Road Riders Ralley they had in Burnett a few years ago. Can't think of his name.

HMMMMMMMMMMMMMMMMMMMM Now thats an idea

I jack-knifed my truck once. Rainy street, brakes just adjusted up on the truck, borrowed trailer with the brakes out of adjustment, idiot in a car deciding to abruptly stop in the middle of the street for no apparent reason (other than my perception of a hope for a big check from my insurance company). I slid past the side of them and into the ditch without making contact. I wasn't wearing a belt and bounced around in the cab like a ping pong ball.

That one experience keeps me from ever wanting to pull a trailer with my bike.