Ok, so maybe the Explanar is a little too ambitious. Hows about a training aid that is smaller but will still contribute to improving your swing? This little beauty has been featured in golf digest and focuses primarily on your wrist.
As I said, your plane is decided by the sum of several parts. One key area is how and when you hinge your wrist. With the aid of this golf swing trainer, you should find that it becomes second nature.
This device clips to your golf club grip and has a small cup sitting just above your wrist. As you bring the club back in your backswing, you can see whether you are cocking your wrists too early or too late. It also lets you see if you bend your wrist too much or too little.
You won’t actually hit on the downswing with this device fitted. It is a device that focuses primarily on the backswing. It won’t cover every element of your swing either; instead, it ensures that you are doing the right thing with your arms.