I reasently I stop playing brawl but I got a friend that have USB loader but we don't know how to use the hack
it all depends on ur usb loader. i use cfg usb loader. anyway u set up the game like u would with gecko with a gct and file directory. next u need to find out how to activate ocarina cheats on ur loader, it's usually pretty easy, and ur set.
note that ur sd card must be under 2 gigs or the files will not be read from it. also usb gecko is a completely different program the gecko os or a usb loader :3