I get up and run a mile before I catch my 7 o'clock bus to school.
Good Lord you're up early.
One of my coaches: You can sleep when you're dead.
I'm not sure what move you're talking about at the end, but I'll address the beginning first before I start listing stuff that you should do to work the omo.
Something I've been having trouble with and maybe you could suggest something:
I almost always work from rubber guard when I'm on the bottom, so I have the opponent broken down... but when I go for the omo plata I have very little control of his posture. At first I thought they just knew what I was going for... and have been using it solely as a transition. Is there some key element to rolling for omo plata and keeping the guy's head controlled? (damn it's hard to describe jiu-jitsu without seeing it) If I do get it, instead of doing the traditional "arm over the back" to situp, I immediately overhook the close leg and pull up that way. When I do that I feel like I'm just overpowering the guy and not using good technique.
As far as breaking down your opponent and working for the omo, it's really about getting your body out from under his center without him turning and pushing his head into you, which can get to be a real problem.
Part of this is leg flexibility, and you really just need to practice working you legs up his back until you're slipping your foot past his head from rubber guard. Still, I know that not everybody is that flexible.
If you're looking for a quick fix, there really isn't one, it's just a slickness issue that you develop over time, but a few key things you might want think about:
Isolate the arm first by putting his hand on the floor. This will make the armlock that much easier to sink in and it will really help you force the head out.
Keep the hips high and the initial twist tight, when you start working for the submission. Some people make the mistake of hesitating, and if you stop in the middle, it's easy for your opponent to adjust his head. Once you've got the arm isolate, really working on keeping those hips tight (which can be done through drills or through training) is really an important factor.
Use your hand to push the head out as you are turning your hips. This will help you get to the leverage you want and finish the submission really tight. Even if he's trying to force his head in, the combination of using your hand to push his head in and using the hand also to adjust your hips out should make getting the position much easier.
If your problem is just keeping a grip on the guys head, that's just a practice thing, too. I don't know what else to say about that. Did I cover your problem?
As far as the finish, grabbing the belt (or the side, in the case of no-gi) isn't the only way to finish. If you go to your back and hook your opponent's leg right under the knee. This hook should be with your inside arm over your head, so that you're touching your shoulder. Make sure that your legs are tight, and do a barrel roll over your side. That's actually a sweep that will put you in sidemount with a different kind of control of the arm. I like to adjust to a reverse triangle from this position and finish with a kimura, but that's just my style.
It sounds like a term that your gym uses, though I'd imagine it's probably just an over-under reversal (or at least that's what it sounds like to me).
Also, I got a belt test today and was going over our requirements... ever heard of a "big boy reversal"?
If you need help with it, take a shot at describing it and I'll see what I can do.