A nurse I knew worked at a summer camp, and the newbie camp helper was letting all the kids pick big bunches of poison ivy as part of a leaf project. When the nurse saw it, she ran to the kitchen for a bottle of dish detergent, ordered every kid into the lake, and had them scrub their affected parts with dish soap. Not one kid developed blisters.
Technu helps get rid of urushiol.
Except, last year and this, it hasn’t helped a bit. Calamine does help. A little.