We had no pools but we had the Potomac and Wicomico to swim in. We always used bottom mud or sand and rubbed it on the sting. Mud was better, although I don't know exactly why.
Nasty critters....
Joe you must live close to me. I am a 7th District boy too. Got many a sting in my time, Shaking those jellyfish out of a haul seine net is a thrill you wont forget. I find Meat tenderiser works pretty good.