Blue Boro powder (if they still make it).
I got it at a drug store. Don't recall if it was on the shelf or behind the counter but it was OTC - no prescription needed.
Mix it in water and put some soaking wet paper towels on the affected areas. fold or use multiple to keep it wet longer.
That was the best I ever found. I bet the steroid pills or shot would work good too.
For next time, learn to ID that evil Spawn of Satin plant and avoid it. OR, if you get it on you or think you have, as soon as you get home, strip down and put your clothes straight in the washer.
Then get a bottle of Dawn dish soap and a wash rag and get in the shower. Scrub every square inch of you with Dawn to wash off the Urushiol oil that causes the irritation.
You have a window of several hours - not sure but maybe 4-6? to get that stuff scrubbed off and you will be fine. Also scrub your boots and any tools using vinyl / rubber / latex gloves to keep it from getting back on you. When i was a kid tramping down the creek bank, my mom would get it just from washing my clothes!

TeleDoc - nearly every insurance carrier has it now.

Yep. Oral steroids like Prednisone will take care of it.

What most people don't realize is that as soon as you take a bath or shower, or wash the area in general, the poison is gone. YOU CANNOT SPREAD IT by popping the pustules or scratching, that is an old wives tail.The spreading that you see is because it entered the body and the body is creating blisters to fight off what it thinks are infected locations even though its not. There is nothing you can do to stop it, the only thing you can do is lessen the itching or numb it. It will run its course in a week for mild cases or two weeks for severe cases.