I spend all summer backing my boat trailers down ramps, and then all winter backing a steerable two-axle wagon (eg. small hay wagon) around a tight 90 bend onto a patio. The boat trailers are like any other, you simply reverse steer in your mind to push the trailer the way you want, pretty simple. The wagon adds a second pivot point, so that you must reverse the "reverse" again, which is somehow even more confusing.
Whereas I was previously to the point where I could do a slalom course in reverse with any regular boat or landscape trailer, so many hundreds of times backing up this little hay wagon with "double-reversed" steering, has me looking at least a little less expert each spring at the boat ramp.
That said, after once or twice with each trailer type, your muscle memory recovers, your brain re-recognizes the patterns it once knew.
One thing I haven't seen pointed out is that, when working with a steerable trailer like my wagon above, or even a very short trailer, it can help to have a very long drawbar on the back of the tractor. I mounted a ball hitch receiver on the back of my
ballast box this reason, getting that ball far enough aft of the rear axle to have some swing. It's the same theory mentioned by a few others above, with putting the ball out front, you need some swing between your pivot (axle) and the ball to effect a satisfactory change in direction with a small movement of your front wheels.