I'm sorry that I can't tell you a natural way to clear this. Will say that the right long sleeved shirt, latex gloves and long pants can offer protection from the poison ivy. Follow up with removing the clothes carefully and showering. And thoroughly wash the clothes before rewearing.

When I deal with poison ivy I use Roundup and then with protective clothes on, ID/pull and bag the dead poison ivy.

Hate that stuff!

HTH,
Rosie

If you want to kill everything and you are not in a hurry, you can weed whack the hill and cover with black plastic and let it cook in the sun. If it's shaded it will take considerably longer. Unfortunately that probably won't kill the poison ivy, it will just creep under the plastic and emerge on the other side. The only way I have found to get rid of poison ivy is roundup. I do "bag" it first (use long gloves as Rosie suggests) and then spray the round-up in the bag and tie it up and leave it for a week. Generally I let poison ivy go unless it's in the garden, the birds really like the berries!

Just a word of caution though, killing all the vegetation on the hill could make the hill erode so don't do anything until you are ready to replant.