I would use the loader. But, I have also used the choke chain to remove brush.
You have multiple obstacles though... First, you gotta get the brush out. Then, you gotta get rid of it. Then, the tractor is going to be covered in the oils from the poison ivy/oak.
Even if you kill it and come back in a few months, the oil will still be in the dead leaves, and especially in the dead twigs and roots.
I have got poison oak from the tractor weeks after the last exposure I had to it. Greasing fittings, changing oil, chaining it on trailer ect.
USTMD has the best idea, but I cannot afford it. So, I take just deal with the itch. I suit up, coveralls, gloves, Avon or Technu pre-exposure cream, Technu after, and a week of itching and oozing sores.
I dont know if it helps, but I spray the tractor with degreaser and power wash it afterwards...