When I was a kid my mom used to use a bar laundry soap called Fels Naptha on the exposed area right away. If it was too late for that & started to blister then it was calamine lotion. (That brings back memories of me & my friends being covered with that bright pink lotion. You could tell we were all playing in the woods together.
If all else fails a soothing solution is a bath with an oatmeal product such as Aveeno bath powder. Just watch it because it makes the bathtub really
Thankfully poison ivy isn't hardy up where I live so we haven't had any trouble with it. My son just moved & is working as a landscaper in an area where it is common & just called to tell me his woes about getting into some poison ivy. Unfortunately it was while working with a chainsaw so he got it but good. A trip to the ER for steroids & antihistamines.
Ah well, hopefully a lesson learned.
Hope this helps & good luck with it!