Congrats on the promotion.
I would suggest you read both the fury guide here, and all the tanking information you can. It's important to know how both sides work, since people very commonly itemize incorrectly with both builds. You'll want to aim them down the right path of what goals to reach in gear and talents, rotations, etc. to get the most out of your raids as you get into harder content.
You also need to set an example. So, don't take offense - I know you didn't ask about this, but I would suggest after reading some guides and such, you switch up your talents and orient them more toward 25 man tanking. If you can impress people by outperforming them, they will come to you and eagerly take your advice.
The biggest thing I find myself doing each raid is just watching newer people's performance. If someone isn't up to par, I talk to them about what I think they could change. Usually, as I said, people don't itemize the best way for the content, or don't use the best rotation. If I can't simply talk to them about it because they need a lot of work, I direct them to this site and tell them to read lots of guides and ask me questions.
It can be annoying to criticize people like that, but as you get into TK and SSC it will actually start to make boss kills not happen. With the enrage timers and whatnot getting harder as you progress, tanks performing their best is a big deal.
Because you have so many tanks, you should probably try to be strict about screening applicants. Take them to a heroic and do some crazy stuff to see how they can handle themselves when things go wrong and stuff happens that they aren't used to. Most heroics are so mechanical to tanks nowadays that it can be done in their sleep - so you have to surprise them.
Right now we take applicants to Gruul kills because it's the easiest content we still do (for the dps trinket), but also tests every type of applicant. It requires good dps, good healing, good threat and survival skills from the tank, and it requires everyone to be situationally aware of their surroundings and forces people to move during the fight. I think it's a great proving ground for applicants, but I don't know how easy the boss is for your guys, so this might not work for you yet. Try to look for fights like it though, so you can test many aspects at once. Movement is a crucial skill that many players new to raiding in BC lack when they have only done Kara, so try to test for that especially.