The idea of canni dancing is to be sitting each tick with a cast of canni between ticks. So tick for regen, canni, sit, next tick for regen. Just as your mana ticks you hit the button and are sitting again for the full regen from the next tick.
/pause X,/cast 9
/sit
[Note: When using a comma the second command goes first. This says: Cast, pause, sit.]
Need to pause between the cast and the sit. X is cast time plus lag. It's been a very long time, but I seem to recall using anywhere from about 12 to 25 for X depending on lag. You want the number to be as small as possible. You can tell the pause is too short if you get a "you can't do that now" message. That means you are still casting when it tries to sit. Pause 60 = 1 tick.
Back in the OLD days we had to /sit off first. You just don't know how easy you whippersnappers have it now. LOL.