1)It used usually and most of the times by body moves. Someone use the hand as he is playing his @@ and move a move upside down like holding the @@....
2)You can use it for telling someone that is stupit or that is saying something stupit.
2)You are taka taka (and you must do the move with the hand in this case.
2)someone is saying something and you just say ''taka taka'' and you make the move with the hand.