Back when I trained for the public and bought, trained and sold a lot of OTTBs and OTTQHs I did the exact same thing. I spent a few days getting more control and guiding working on them and then I headed to the hills. I trained a lot of Arabs for the public for trail riding (mostly competitive), for flat racing and for showing. I did the exact same thing with them. for me to get the most done with them, I wanted them really 'broke' first. That meant going to the mountains. I lived across one irrigation canal from BLM, National Forest and not very far from 2 Wilderness areas that extended well above timber line. I could ride over 3 million acres without hitting a fence. I had the brokest, least spooky hot-bloods in the country. I was coming back to the ranch and starting TBs over fences in brief rides after returning from the trails. [Oh, and did I mention that many of them were stallions, particularly Arabs. It was years before anyone sent me an Arabian gelding. I did not think these people owned knives or knew Vets castrated horses back then]
These horses rode like they had had a year or more of training after 60 days or less. I was selling hunter, jumping and dressage prospects and people would not believe me how recently they had raced. They were quiet, willing and very controllable. They would all ride on a long, loose rein. Very few were spooky at all. People that do not think this works just have not done it and have babied horses along for months or years. A few wet saddle blankets and long rides out in the rough country would have had them riding like a totally different horse. They come back to the ranch on a long, loose rein, walking out with a low flat neck and are sure not hunting boogers. You just cannot get this done in an arena.
Oh! and by the way, I did little or no ground work other than training them to move when a where I wanted (most track horses already did this) and teaching them to longe. Well, many of the Arabians had been pets so they took a little more mannering. Come to think of it, the term 'ground work' had not been coined back then. I just called it 'mannering' them and breaking them to longe. It took all of a day or two.