That sound is purely un-labial. Make a loose circle out of your tongue and hard palate and just blow out. It should sound like you are encouraging a horse to go. Hyea!
Do any of you gentlemen perchance have a spare job?
If anybody really believed this bullshit you'd think they'd take the idea of damning somebody a little more seriously. Like I get that sometimes a motherfucker just HAS to be thrown into a lake of fire, but you don't have to like it. Or write a jaunty song about it.
They were killed for saying "go on up" which totally means "fucking die, prophet and by extension all-mighty god/jesus!" They then added "you bald head" or words to those effect, but that was just a misdemeanor tacked on to a capital charge.