The only things I know, are that you should do it when the opponent is at the lowest stamina level possible. And you don't have to 'mash' the buttons and twirl the right stick at the same time, wow that sounds hard, you only have to do one or the other. If your character has high submission stats, use the stick, if he has low submissions and high strength use the button mashing.
Nobody F's with the Jesus
(Sig by Killz cause of boatoar)
FFL: Silva, Silva, Nogueira, Nogueira & Franklin