It’s the start of the summer diving season and it's always a good idea to review DAN's articles and FAQs on Diving Medicine. DAN’s web site has an enormous amount of information and really great articles.
The latest jelly fish sting first-aid can be found in the FAQ at http://www.diversalertnetwork.org/medical/faq/faq.aspx?faqid=96
which is slightly different than the first-aid described in the medicine article. I believe the FAQ is the correct first-aid.