If its the one that Glitch is talking about you just throw the ball over the barrier. You have to let go when the Miis hand reaches its highest point. Its quite easy really
If lane 12 is the one that has the 3 small barriers right in the middle, all in a line... here is what I do.
I'm right handed...
Move my mii to the far right, so that the straight aiming line is lined up on the last board. If I threw the ball straight here, it would ride the edge of the gutter the whole way.
Now I angle it about 2 clicks to the left. It will be aiming just to the right side of the last barrier.
I make a very slow throw. I rotate my wrist way to the left and let go when the ball is coming down to the floor. I don't want any loft/lob on the ball.
When I say I 'rotate' my wrist.. that is what I mean. I don't twist it. I rotate my whole arm almost. When I let go, the back side of my hand is facing the ceiling and the sensor part of the remote (the end) is pointing to the left. In other words, make a fist and give a 'thumbs up'. Rotate your hand so that your thumb points left, parallel with the floor. This is how I am holding the remote when I release the ball.
The key for me has been to do it really slowly. The ball seems to spin a lot more this way. Hope this helps.
Here is what i do for lane 12. Im right handed. I go to the right so my straight line aiming is parallel to the right side of all the barriers on the outside of them. Then i adjust my angled aiming 2 clicks to the right so to be aiming for gutter. Now the hard part. I flick my wrist when i release the ball so to get alot of curl on the ball. If you manage to curl it properly it will go right around all the barriers. Im platinum on this training excersise. If you think the curl is difficult on this one wait till u get to lane 19 if you need more help on this excersise let me know