The easiest way, is to grab the steering wheel like you always do, adjust your mirrors like you always do, and then put the truck in reverse.
Now, when backing up, look in the outside mirrors, and remember this....TURN TOWARDS TROUBLE.....in other words, when backing up, if the trailer/boat is getting close to hitting something, turn towards that side.
No special hand positions, no special remembering to turn the opposite way.....while backing up, if the trailer is gonna hit something on the drivers side, turn the truck like you would if you were turning left when driving normal in a forward direction.....if it is gonna hit on the passengers side, turn the truck right like normal when moving forward.
Try it in an open parking lot....is is much easier than the other methods.
I even have a backup camera, and I only use it to hook to the trailer, or when getting close, otherwise, I use the side mirrors.
Towing mirrors would be better, but normal ones will work too.
The real challenge is when the trailer is empty......do the same thing, but you have to pay more attention as it is harder to see.
I use to turn around & put my head up against the headliner to see my empty trailer with my 3500 dually, and that was WITH the tailgate down. It also had towing mirrors, but they didn't help with the pregnant hips on the bed.