Urishiol is soluble in paint thinner. I use one of the green abrasive scrubbies dipped in thinner followed by old fashioned saddle soap. It goes without saying that you should wear rubber gloves to do this.

If your suffering from the "rash" take 1000mg of vitamin "C" four times a day,its a natural antihystemine.
Since I've started doing this (I get into the ivy 4 or 5 times a season) i barely break out in a rash and its gone in three days and I don't itch. No dozing off like Benedryl either. have fun

How do you keep the paint thinner from soaking into the leather? How does this method get the ivy oil out of the leather?

What about scrubbing them down with Tecnu?

You don't think the leather absorbed the oils all the way to the inside, do you?