More practice!
These "adventure" type trailers can be PITA to back up, but it is not impossible. It just takes a bit of practice and patience. I learned pushing M101A1/2/3's around behind various HMMWVs, so the short axle to pintle was a bit easier for me. The best way to control it is to make VERY small inputs with the steering, as they jack-knife very quickly. Place one hand at the bottom of your steering wheel, and push it in the direction you want to trailer to go, by doing this you take some of the guess-work out of the backing AND minimize steering input.
Patience + Practice. this will also help you down the road on the trail, when you may NEED to back the trailer into a precarious position and don't have the crutch of a trailer dolly.