If it's version 10 there should be a video on how to do it. I myself watched Nickaboo92's tutorial on youtube. If you are running 10.5 then maybe the gym changed if it did change I guess go through by trial and error.
Are you using 10.5? Some of his pokemon receive a fairy type so dark types are less valuable now. You should get a steel type to deal with those. In the long run I found Sharpedo to be useful if you need a water type!
So apparently it's in the warehouse in the coral ward but does any one know if there are certain conditions for it to appear? I really want a Blissey as a tank so I can stall in case i need to heal or something.
So um... this Smogon site would it happen to be Smogon university? Honestly i didn't really see to many stuck up pricks there. (Maybe 'cause I was asking them about their opinion on teams.)
*Edit* Yeah they're a bunch of stuck up pricks... :/