The Asian version of the game is the only one you could do the soul glitch if you erase the patch and do it offline. The American version of the game already came patched within the game so it's impossible to erase the patch like on the Asian version.
And the Soul Sucker Exploit is when you manage to find someone who will help you as a black phantom (or you help him/her as a black phantom). It's almost impossible but if you have the Duel stone it makes things a lot more easy.
WITHOUT A DUEL STONE:
You wold need to be invaded or invade and quickly message the host/invader to try to make him/her cooperate. (this is the hardest part, normally one of you will end up dead within seconds of seeing each other).
Then the player with the body casts soul sucker on the Black Phantom 'till it's heart's content.
When he's done the Black Phantom player should turn off his/her Playstation or pull the cord so the conection fails and the game doesn't have time to save the changes, therefore avoiding any soul losses for the Black Phantom.
WITH A DUEL STONE:
It's way more easy.
Find a friend around your soul lvl.
Pull the plug/Turn off the console/etc