Tip from the Pro:
You can go to a doc at anytime, drop your copay, tell him/her that you are deathly allergic to urushiol and related poison oils - tell em' to stock you up with a prescription that you may fill whenever you like (it is in their best interest, remind them they would rather see you now than when it is in your eyes or other painful areas).
Carry a z-pack in your bag - pop a couple if you feel like you have come in contact with the stuff. Carry Tecnu on your person, lather up post round and be sure to wash off within a few hours (see previous post re: the original intention of Tecnu). Remember to use Tecnu on any and everything that may have come in contact with the PI, or that you may have inadvertently touched after coming in contact with PI.
If already infected, I recommend continuing to use Tecnu as a body wash as it will continue to remove the oils oozing out onto your skin. Zanfel is good for when you just have to scratch (don't actually scratch, allow the exfoliates to do their job). While in the shower, expose the areas to the HOTTEST water possible, not the hottest you can stand, the hottest POSSIBLE - crank the water heater up if necessary. Outside of the shower, when you get that itch, grab some ice cubes and rub on the infected area.
I haven't had a PI infection in quite some time. Call me sick, call me demented - but I sometimes miss the sensation of scalding hot water on the infected areas... Feels sofa king good.