Actually, if you are planning to do technical training, I think that getting a set of doubles and diving them for a while before the class is ideal. Such classes, if well taught, are difficult enough, without adding the stress of unfamiliar gear to the mix.
You can dive manifolded doubles as a big single tank (if you haven't learned how to do shutdowns) with the awareness that you have many more failure points, but with the same strategy as singles -- major failure, abort the dive and surface. I swam my doubles around for a few weeks before I tried a valve drill in them.
Do be aware, though, that the danger people are describing is REAL. When you DO start doing valve shutdowns, you WILL almost certainly turn off all your own gas at some point. And when you take your tech training, if you have buddies, it's not at all unlikely that one of THEM will turn off the gas you are breathing at some point. So I would say that, until you are quite facile with the drills AND have proved to yourself that you are calm and methodical when faced with no gas, it's not a good idea to do valve drills without a buddy who is experienced in them, and it's not a good idea to use double tanks for redundancy on solo dives.
You can dive manifolded doubles as a big single tank (if you haven't learned how to do shutdowns) with the awareness that you have many more failure points, but with the same strategy as singles -- major failure, abort the dive and surface. I swam my doubles around for a few weeks before I tried a valve drill in them.
Do be aware, though, that the danger people are describing is REAL. When you DO start doing valve shutdowns, you WILL almost certainly turn off all your own gas at some point. And when you take your tech training, if you have buddies, it's not at all unlikely that one of THEM will turn off the gas you are breathing at some point. So I would say that, until you are quite facile with the drills AND have proved to yourself that you are calm and methodical when faced with no gas, it's not a good idea to do valve drills without a buddy who is experienced in them, and it's not a good idea to use double tanks for redundancy on solo dives.