If you're basically at the end game and struggling to come across enemies often I recommend fast travelling to Rae-Rae's Pumpkin Farm (Northern part of John's region). There will be 1-2 enemies that spawn here, they will spot you as you run over the the car spawn location.
After you've killed these guys simply use the fast travel here again (you don't have to travel elsewhere first)
I used the meat grinder tractor for this as it links with another trophy and it seemed to smash through fences easier which the enemies will sometimes take cover behind.
Feel free to comment any suggestions