explaining this to the player visually is quite tricky.
programming-wise, i would create a sprite as collision area where your finger has to stay.
as long as the finger is on collision with the sprite, the blade keeps swinging.
when removing the finger from the sprite, you create a text object with the text you want and pause the game by using the command "set time scale = 0"
once collision with the sprite is true again, set time scale to 1 again and delete the text.
you probably need to create different groups and/or variables to track the different situations your are in