The general rule of thumb in the FMA, especially the ones that work a lot of knife, is to avoid switching hands. It may look flashy and cool but practically speaking, you're asking to be stuck. Unless you're superbly coordinated and well mastered, switching hands should be used only when necessary, like when you and your opponent are in a bind or you can foresee that a bind is inevitable - but even then, you're gambling. Otherwise, you're opponent may easily knock your weapon out of the air or prevent the other hand from catching the weapon all together, and maybe even simultaneously control the now empty lead hand and slash and thrust before you know it.
I've seen switching hands for sticks too, like the clip below. The drill may be great for hand-eye coordination and timing, but you should also critique its use combatively. Not saying the teacher in the clip doesn't, but I just want expound on that here. I make it a rule to always critique clips with my teacher and students. That is how you will grow. If your teacher doesn't do this then do it on your own. You should always be questioning and seeking the truth in any application. Learning to recognize is key - recognition should be a part of coordination and timing. If you watch the clip closely, you will recognize how smoothly the transition goes from one hand to the other. But can you see where you might break the flow - practically and combatively speaking? I would say just as the stick makes the transition you will find a tiny opening. Do not let the now free lead empty hand parry. Why? Because you "will miss all the heavenly glory" - just kidding. Because you will recognize that by his abandoning the front guard, you can now thrust to the eye (the moon) before he gets a chance to counter with the stick in his left hand. Because you are now controlling the lead hand, you have the added safety net of using it (his own hand/arm) to block his left hand strikes.
This is just one of many possibilities. Seek for yourself all other avenues and see if you will reach the same goal - and counter any obstacles along the way.
What to Keep in Mind When Switching Hands
