Multiverse, gamemodes, and ranks help needed!

Players are able to go into the portal, but then they don't have a rank in that world so they can't go back through it. I set it so that everyone can use the portals, so that works fine. However I want to set it so that for one certain portal only one person is able to go through it. I know that you can give private permissions to a player based on their world, but I guess I'm wondering how to give someone a rank in a different world? When I try and give them a rank (/manuadd <user> Spleef) then they still don't receive it. Is there a way to set so that players will get a certain rank when going into a world? Or set it so that only one person can enter a world? (Of course OP's can, but I mean for normal players)

Sorry there are so many questions in no particular order, I hope you can sort of understand my situation here. Thanks!

If you can help please add me on Skype: theoceansharma