Lol towing a double is 2x as much effort than a single trailer. A good friend does the double haul 2-3 times a yr. It's not easy and his 2nd trailer is a 1000lb racing Catamaran, not a heavy power boat. The big issue is length it's a major undertaking once you exit the highway, unless your in bfe all the time.
It's not that difficult, with the proper training
I routinely drive my AWD motor home towing a 30' trailer and that can be interesting. Driving my two axle tractor towing double trailers is a lot easier to maneuver, except in reverse.
The key to driving either is preplanning your route. If you stay with the 18 wheelers it is not to difficult
You need a smart phone, tablet or laptop with internet connection to look at the aerial photos, I love google maps.
You will also need one of these