*If you want just your question answered just read the last paragraph*
If someone is leading heavy on either foot, the low single is always there. So that is a good option. Especially when people realize you lead with the other leg, their stance usually changes. They usually lead with their front leg more against a lefty. This opens up the low single ala Randy Couture/James Toney. Change your level ALL THE WAY DOWN to all fours, and you kind of lunge in. The key is getting your hand around his heel AND your elbow down. We call this picture-framing the foot (for obvious reasons). This keeps their ankle stuck in place so they can't kick out. Your forehead is on the inside of their knee cap, and you want to push your head in and keep your hand planted and get him onto his hip. You won't always get him onto his hip though. Once you are in the right position, you need to make sure your right hand catches his hip. You will feel this from wrestling. Perfect low single here at 1:50 (and a replay at around 4:30 after the first period ends):
http://www.youtube.com/watch?v=fQ4WhcefpNs
Definitely work on your sweep single to their right leg. To set it up, i would use an arm drag in a right collar tie. Once you are in the tie, you take your left hand and knock their up a little to get it off your neck and break the tie, then you drag it down and away with your right hand. Your left hand is free to shoot a perfect single. We used to call this "wax on and wax off". If you look up arm drags, I am sure you can find what I am talking about.
And remember, circle away and shoot on the sweep single. My wrestling coach was a Senior Nationals champion in high school and all he did was shoot singles. He would circle away, circle away, and wait until you step with that foot. He would change his angle and shoot a sweep single. Circle away, wait for the right look, maybe throw in a few fakes, and then shoot back. Never circle TOWARDS your shot.
For a high crotch that is easy for leftys to pick up, you could work a right leg lead high-c single leg to their right leg. You can just keep your head on the inside the whole time. It is similar to a single leg. So you shoot similarly to a high C, but you keep your head on the inside the whole time, and change off to single immediately.
Other than that though, it is not about the shot, but the setup. Under hooks, and elbow passes are good setups, obviously once you have gotten their leg to come forward. Work on your hand fighting (tying up) to work on getting on the inside. This way you can dictate the tie and take one that is more advantageous to you.
For the question you asked:
That being said, I would look to collar tie with your left arm. He needs to match your tie so you are both have left collar ties. You have to get that leg forward first. You can do that by moving him, snapping his head, or circling away. You need to get him in a square stance. From there you can dig an underhook and throw it by as you shoot. Or you can grip his elbow with your thumb out on the arm he has tied up, and pass the arm by right into your high crotch with your hand that was tied up. That is the best I can do for you. As a wrestling coach, I have my left leg leaders work on low single, sweep single, and then those two setups.
If you need clarification on anything, just send me a PM or something.
