Harry waited, understanding only too well Sirius' position when he ran off to check on his husband. He also understood that he should have stayed put, and knew Moody might have a thing or two to say later.
"I'll give you the list of those who knows how to do the spell," he said. "As for whom has experience, that would be a much shorter list. Not too many have Azkaban duty, but I could probably swing a decent list of who has had it from memory so I'll make you one of that too. From the second war I'd say everyone knows how it feels to have one or two around, seeing how we had Dementors stationed around school, but to have one around and to drive this many off - or at least keep them at bay - is an entirely different thing."
He smiled when Jamie said the trainers were about to tell Moody to sod off, but he agreed that it was vital that people learnt. "There are ways to train the Patronus with the feeling of a Dementor around without there actually being a Dementor around," he said. "Remus used a Boggart to help me train when I was a kid, which granted is helped by the fact that my Boggart is a Dementor. I'm not sure how it would translate to a room filled with people with different Boggart shapes, but perhaps if I'm close enough I can get it to keep it's shape?" He shrugged. "It could be worth a try and if it works we can ask around and see if there is anyone else who can help."